XuDeveloper.github.io/posts/3435cf36.html at master · XuDeveloper/XuDeveloper.github.io

History

1021 lines (488 loc) · 121 KB

Raw

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

647

648

649

650

651

652

653

654

655

656

657

658

659

660

661

662

663

664

665

666

667

668

669

670

671

672

673

674

675

676

677

678

679

680

681

682

683

684

685

686

687

688

689

690

691

692

693

694

695

696

697

698

699

700

701

702

703

704

705

706

707

708

709

710

711

712

713

714

715

716

717

718

719

720

721

722

723

724

725

726

727

728

729

730

731

732

733

734

735

736

737

738

739

740

741

742

743

744

745

746

747

748

749

750

751

752

753

754

755

756

757

758

759

760

761

762

763

764

765

766

767

768

769

770

771

772

773

774

775

776

777

778

779

780

781

782

783

784

785

786

787

788

789

790

791

792

793

794

795

796

797

798

799

800

801

802

803

804

805

806

807

808

809

810

811

812

813

814

815

816

817

818

819

820

821

822

823

824

825

826

827

828

829

830

831

832

833

834

835

836

837

838

839

840

841

842

843

844

845

846

847

848

849

850

851

852

853

854

855

856

857

858

859

860

861

862

863

864

865

866

867

868

869

870

871

872

873

874

875

876

877

878

879

880

881

882

883

884

885

886

887

888

889

890

891

892

893

894

895

896

897

898

899

900

901

902

903

904

905

906

907

908

909

910

911

912

913

914

915

916

917

918

919

920

921

922

923

924

925

926

927

928

929

930

931

932

933

934

935

936

937

938

939

940

941

942

943

944

945

946

947

948

949

950

951

952

953

954

955

956

957

958

959

960

961

962

963

964

965

966

967

968

969

970

971

972

973

974

975

976

977

978

979

980

981

982

983

984

985

986

987

988

989

990

991

992

993

994

995

996

997

998

999

1000

<!DOCTYPE html>

var NexT = window.NexT || {};

var CONFIG = {

root: '/',

scheme: 'Pisces',

version: '5.1.3',

sidebar: {"position":"left","display":"post","offset":12,"b2t":false,"scrollpercent":true,"onmobile":true},

fancybox: true,

tabs: true,

motion: {"enable":true,"async":false,"transition":{"post_block":"fadeIn","post_header":"slideDownIn","post_body":"slideDownIn","coll_header":"slideLeftIn","sidebar":"slideUpIn"}},

duoshuo: {

userId: '0',

author: '博主'

algolia: {

applicationID: '',

apiKey: '',

indexName: '',

hits: {"per_page":10},

labels: {"input_placeholder":"Search for Posts","hits_empty":"We didn't find any results for the search: ${query}","hits_stats":"${hits} results found in ${time} ms"}

}

};

</script>

<title>Android AccessibilityService机制源码解析 | Xu的博客</title>

</head>

Xu的博客

</a>

</div>

</div>

</button>

</div>

首页

</a>

</li>

标签

</a>

</li>

分类

</a>

</li>

归档

</a>

</li>

</ul>

</nav>

</div>

</header>

<h1 class="post-title" itemprop="name headline">Android AccessibilityService机制源码解析</h1>

发表于

2018-06-18

</time>

|

分类于

Android

</a>

|

阅读次数:

</div>

</header>

<h4 id="一、本文需要解决的问题"><a href="#一、本文需要解决的问题" class="headerlink" title="一、本文需要解决的问题"></a>一、本文需要解决的问题</h4>之前本人做了一个项目，需要用到AccessibilityService这个系统提供的拓展服务。这个服务本意是作为Android系统的一个辅助功能，去帮助残疾人更好地使用手机。但是由于它的一些特性，给很多项目的实现提供了一个新的思路，例如之前大名鼎鼎的微信抢红包插件，本质上就是使用了这个服务。我研究AccessibilityService的目的是解决以下几个我在使用过程中所思考的问题：

<ol>

<li>AccessibilityService这个Service跟一般的Service有什么区别？</li>

<li>AccessibilityService是如何做到监控并捕捉用户行为的？</li>

<li>AccessibilityService是如何做到查找控件，执行点击等操作的？</li>

</ol>

<h4 id="二、初步分析"><a href="#二、初步分析" class="headerlink" title="二、初步分析"></a>二、初步分析</h4>本文基于Android 7.1的源码对AccessibilityService进行分析。 为了更好地理解和分析代码，我写了一个demo，如果想学习具体的使用方法，可以参考Google官方文档<a href="https://developer.android.com/reference/android/accessibilityservice/AccessibilityService.html" target="_blank" rel="noopener">AccessibilityService</a>。本文不做AccessibilityService的具体使用教程。

<h5 id="创建AccessibilityService"><a href="#创建AccessibilityService" class="headerlink" title="创建AccessibilityService"></a>创建AccessibilityService</h5><figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 </pre></td><td class="code"><pre>public class MyAccessibilityService extends AccessibilityService { private static final String TAG = "MyAccessibilityService"; @Override public void onCreate() { super.onCreate(); Log.i(TAG, "onCreate"); } @Override public void onAccessibilityEvent(AccessibilityEvent event) { int eventType = event.getEventType(); switch (eventType) { case AccessibilityEvent.TYPE_VIEW_CLICKED: // 捕获到点击事件 Log.i(TAG, "capture click event!"); AccessibilityNodeInfo nodeInfo = getRootInActiveWindow(); if (nodeInfo != null) { // 查找text为Test!的控件 List<AccessibilityNodeInfo> button = nodeInfo.findAccessibilityNodeInfosByText("Test!"); nodeInfo.recycle(); for (AccessibilityNodeInfo item : button) { Log.i(TAG, "long-click button!"); // 执行长按操作 item.performAction(AccessibilityNodeInfo.ACTION_LONG_CLICK); } } break; default: break; } } @Override public void onInterrupt() { Log.i(TAG, "onInterrupt"); } } </pre></td></tr></table></figure>

<h5 id="AccessibilityService配置"><a href="#AccessibilityService配置" class="headerlink" title="AccessibilityService配置"></a>AccessibilityService配置</h5>res/xml/accessibility_service_config.xml <figure class="highlight xml"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 </pre></td><td class="code"><pre><?xml version="1.0" encoding="utf-8"?> <accessibility-service xmlns:android="http://schemas.android.com/apk/res/android" android:accessibilityEventTypes="typeAllMask" android:accessibilityFeedbackType="feedbackSpoken" android:accessibilityFlags="flagRetrieveInteractiveWindows|flagRequestFilterKeyEvents" android:canRequestFilterKeyEvents="true" android:canRetrieveWindowContent="true" android:description="@string/app_name" android:notificationTimeout="100" android:packageNames="com.xu.accessibilitydemo" /> </pre></td></tr></table></figure>

<h5 id="在manifest中进行注册"><a href="#在manifest中进行注册" class="headerlink" title="在manifest中进行注册"></a>在manifest中进行注册</h5><figure class="highlight xml"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 </pre></td><td class="code"><pre><service android:name=".MyAccessibilityService" android:enabled="true" android:exported="true" android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE"> <intent-filter> <action android:name="android.accessibilityservice.AccessibilityService"/> </intent-filter> <meta-data android:name="android.accessibilityservice" android:resource="@xml/accessibility_service_config"/> </service> </pre></td></tr></table></figure>

<h5 id="创建一个text为Test-的button控件，设置监听方法"><a href="#创建一个text为Test-的button控件，设置监听方法" class="headerlink" title="创建一个text为Test!的button控件，设置监听方法"></a>创建一个text为Test!的button控件，设置监听方法</h5><figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 </pre></td><td class="code"><pre>public class MainActivity extends AppCompatActivity { private static final String TAG = "MainActivity"; private Button button; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); button = findViewById(R.id.button); button.setOnLongClickListener(new View.OnLongClickListener() { @Override public boolean onLongClick(View v) { Log.i(TAG, "onLongClick"); return false; } }); } } </pre></td></tr></table></figure>

<h5 id="开启AccessibilityService"><a href="#开启AccessibilityService" class="headerlink" title="开启AccessibilityService"></a>开启AccessibilityService</h5>AccessibilityService服务具体开启位置在设置–无障碍中。

<h5 id="运行应用，点击text为Test-的按钮"><a href="#运行应用，点击text为Test-的按钮" class="headerlink" title="运行应用，点击text为Test!的按钮"></a>运行应用，点击text为Test!的按钮</h5>会出现以下的日志： <img src="https://upload-images.jianshu.io/upload_images/1963233-23d8f1dfce6d7009.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1000" alt="log.png">

具体解释： 点击按钮即产生TYPE_VIEW_CLICKED事件 –> 被AcceesibilityService捕获 –> 捕获后执行长按按钮操作 –> 执行长按回调方法。

为什么AcceesibilityService能捕获并执行其他操作呢，接下来我将对源码进行解析~

<h4 id="三、源码解析"><a href="#三、源码解析" class="headerlink" title="三、源码解析"></a>三、源码解析</h4><h6 id="AccessibilityService内部逻辑"><a href="#AccessibilityService内部逻辑" class="headerlink" title="AccessibilityService内部逻辑"></a>AccessibilityService内部逻辑</h6><h6 id="AccessibilityService-java"><a href="#AccessibilityService-java" class="headerlink" title="AccessibilityService.java"></a>AccessibilityService.java</h6><figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 </pre></td><td class="code"><pre>public abstract class AccessibilityService extends Service { // 省略代码 public abstract void onAccessibilityEvent(AccessibilityEvent event); public abstract void onInterrupt(); @Override public final IBinder onBind(Intent intent) { return new IAccessibilityServiceClientWrapper(this, getMainLooper(), new Callbacks() { @Override public void onServiceConnected() { AccessibilityService.this.dispatchServiceConnected(); } @Override public void onInterrupt() { AccessibilityService.this.onInterrupt(); } @Override public void onAccessibilityEvent(AccessibilityEvent event) { AccessibilityService.this.onAccessibilityEvent(event); } @Override public void init(int connectionId, IBinder windowToken) { mConnectionId = connectionId; mWindowToken = windowToken; // The client may have already obtained the window manager, so // update the default token on whatever manager we gave them. final WindowManagerImpl wm = (WindowManagerImpl) getSystemService(WINDOW_SERVICE); wm.setDefaultToken(windowToken); } @Override public boolean onGesture(int gestureId) { return AccessibilityService.this.onGesture(gestureId); } @Override public boolean onKeyEvent(KeyEvent event) { return AccessibilityService.this.onKeyEvent(event); } @Override public void onMagnificationChanged(@NonNull Region region, float scale, float centerX, float centerY) { AccessibilityService.this.onMagnificationChanged(region, scale, centerX, centerY); } @Override public void onSoftKeyboardShowModeChanged(int showMode) { AccessibilityService.this.onSoftKeyboardShowModeChanged(showMode); } @Override public void onPerformGestureResult(int sequence, boolean completedSuccessfully) { AccessibilityService.this.onPerformGestureResult(sequence, completedSuccessfully); } }); } } </pre></td></tr></table></figure>

分析：

<ol>

<li>AccessibilityService是一个抽象类，继承于Service，提供两个抽象方法 onAccessibilityEvent() 和 onInterrupt()；</li>

<li>虽然是抽象类，但是实现了最重要的 onBind() 方法，在其中创建了一个IAccessibilityServiceClientWrapper对象，实现Callbacks接口中的抽象方法。</li>

</ol>

<h6 id="IAccessibilityServiceClientWrapper"><a href="#IAccessibilityServiceClientWrapper" class="headerlink" title="IAccessibilityServiceClientWrapper"></a>IAccessibilityServiceClientWrapper</h6><figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 </pre></td><td class="code"><pre>// 以分析onAccessibilityEvent为例，省略部分代码 public static class IAccessibilityServiceClientWrapper extends IAccessibilityServiceClient.Stub implements HandlerCaller.Callback { private final HandlerCaller mCaller; private final Callbacks mCallback; private int mConnectionId; public IAccessibilityServiceClientWrapper(Context context, Looper looper, Callbacks callback) { mCallback = callback; mCaller = new HandlerCaller(context, looper, this, true /*asyncHandler*/); } public void init(IAccessibilityServiceConnection connection, int connectionId, IBinder windowToken) { Message message = mCaller.obtainMessageIOO(DO_INIT, connectionId, connection, windowToken); mCaller.sendMessage(message); } // 省略部分代码 public void onAccessibilityEvent(AccessibilityEvent event) { Message message = mCaller.obtainMessageO(DO_ON_ACCESSIBILITY_EVENT, event); mCaller.sendMessage(message); } @Override public void executeMessage(Message message) { switch (message.what) { case DO_ON_ACCESSIBILITY_EVENT: { AccessibilityEvent event = (AccessibilityEvent) message.obj; if (event != null) { AccessibilityInteractionClient.getInstance().onAccessibilityEvent(event); mCallback.onAccessibilityEvent(event); // Make sure the event is recycled. try { event.recycle(); } catch (IllegalStateException ise) { /* ignore - best effort */ } } } return; // ... } } } </pre></td></tr></table></figure>

分析：

<ol>

<li>IAccessibilityServiceClientWrapper继承于IAccessibilityServiceClient类，它是一个aidl接口，同时注意到它是继承于IAccessibilityServiceClient.Stub类，可以大概猜测到，AccessibilityService为一个远程Service，使用到跨进程通信技术，后面我还会继续分析这个；</li>

<li>IAccessibilityServiceClientWrapper的类构造方法中，有两个比较重要的参数，一个是looper，另一个是Callbacks callback。Looper不用说，而Callbacks接口定义了很多方法，代码如下：

</li>

<li>IAccessibilityServiceClientWrapper同时也实现了HandlerCaller.Callback接口，HandlerCaller类通过命名也可以知道，它内部含有一个Handler实例，所以可以把它当做一个Handler，而处理信息的方法就是HandlerCaller.Callback#executeMessage(msg)方法

</li>

<li>代码有点绕，故简单总结一下流程： AccessibilityEvent产生   -> Binder驱动    -> IAccessibilityServiceClientWrapper#onAccessibilityEvent(AccessibilityEvent)     -> HandlerCaller#sendMessage(message); // message中包括AccessibilityEvent      -> IAccessibilityServiceClientWrapper#executeMessage();       -> Callbacks#onAccessibilityEvent(event);        -> AccessibilityService.this.onAccessibilityEvent(event);</li>

</ol>

到这里解决了我们的第一个问题：AccessibilityService同样继承于Service类，它属于远程服务类，是Android系统提供的一种服务，可以绑定此服务，用于捕捉界面的一些特定事件。

<h6 id="AccessibilityService外部逻辑"><a href="#AccessibilityService外部逻辑" class="headerlink" title="AccessibilityService外部逻辑"></a>AccessibilityService外部逻辑</h6>前面分析了接收到AccessibilityEvent之后的代码逻辑，那么，这些AccessibilityEvent是怎样产生的呢，而且，在回调执行之后是怎么做到点击等操作的（如demo所示）？我们接下来继续分析相关的源码~

我们从demo作为例子开始入手，首先我们知道，一个点击事件的产生，实际代码逻辑是在View#onTouchEvent() -> View#performClick()中： <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 </pre></td><td class="code"><pre>public boolean performClick() { final boolean result; final ListenerInfo li = mListenerInfo; if (li != null && li.mOnClickListener != null) { playSoundEffect(SoundEffectConstants.CLICK); li.mOnClickListener.onClick(this); result = true; } else { result = false; } // ！！！ sendAccessibilityEvent(AccessibilityEvent.TYPE_VIEW_CLICKED); return result; } </pre></td></tr></table></figure>

这里找到一个重点方法sendAccessibilityEvent()，继续跟进去，最后走到View#sendAccessibilityEventUncheckedInternal()方法： <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 </pre></td><td class="code"><pre>public void sendAccessibilityEventUncheckedInternal(AccessibilityEvent event) { if (!isShown()) { return; } onInitializeAccessibilityEvent(event); // Only a subset of accessibility events populates text content. if ((event.getEventType() & POPULATING_ACCESSIBILITY_EVENT_TYPES) != 0) { dispatchPopulateAccessibilityEvent(event); } // In the beginning we called #isShown(), so we know that getParent() is not null. getParent().requestSendAccessibilityEvent(this, event); } </pre></td></tr></table></figure>

这里的getParent()会返回一个实现ViewParent接口的对象。 我们可以简单理解为，它会让View的父类执行requestSendAccessibilityEvent()方法，而View的父类一般为ViewGroup，我们查看ViewGroup#requestSendAccessibilityEvent()方法 <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 </pre></td><td class="code"><pre>@Override public boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event) { ViewParent parent = mParent; if (parent == null) { return false; } final boolean propagate = onRequestSendAccessibilityEvent(child, event); if (!propagate) { return false; } return parent.requestSendAccessibilityEvent(this, event); } </pre></td></tr></table></figure>

这里涉及到一个变量mParent，我们要找到这个mParent变量是在哪里被赋值的。 首先我们在View类中找到一个相关的方法View#assignParent()： <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 </pre></td><td class="code"><pre>void assignParent(ViewParent parent) { if (mParent == null) { mParent = parent; } else if (parent == null) { mParent = null; } else { throw new RuntimeException("view " + this + " being added, but" + " it already has a parent"); } } </pre></td></tr></table></figure>

但是View类中并没有调用此方法，猜测是View的父类进行调用。 通过对源码进行搜索，发现最后是在ViewRootImpl#setView()中进行调用，赋值的是this即ViewRootImpl本身。 直接跳到ViewRootImpl#requestSendAccessibilityEvent()方法： <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 </pre></td><td class="code"><pre>@Override public boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event) { if (mView == null || mStopped || mPausedForTransition) { return false; } // Intercept accessibility focus events fired by virtual nodes to keep // track of accessibility focus position in such nodes. final int eventType = event.getEventType(); switch (eventType) { case AccessibilityEvent.TYPE_VIEW_ACCESSIBILITY_FOCUSED: { final long sourceNodeId = event.getSourceNodeId(); final int accessibilityViewId = AccessibilityNodeInfo.getAccessibilityViewId(sourceNodeId); View source = mView.findViewByAccessibilityId(accessibilityViewId); if (source != null) { AccessibilityNodeProvider provider = source.getAccessibilityNodeProvider(); if (provider != null) { final int virtualNodeId = AccessibilityNodeInfo.getVirtualDescendantId(sourceNodeId); final AccessibilityNodeInfo node; if (virtualNodeId == AccessibilityNodeInfo.UNDEFINED_ITEM_ID) { node = provider.createAccessibilityNodeInfo(AccessibilityNodeProvider.HOST_VIEW_ID); } else { node = provider.createAccessibilityNodeInfo(virtualNodeId); } setAccessibilityFocus(source, node); } } } break; // 省略部分代码 } // ！！！ mAccessibilityManager.sendAccessibilityEvent(event); return true; } </pre></td></tr></table></figure>

重点：AccessibilityManager#sendAccessibilityEvent(event) <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 </pre></td><td class="code"><pre>public void sendAccessibilityEvent(AccessibilityEvent event) { final IAccessibilityManager service; final int userId; synchronized(mLock) { service = getServiceLocked(); if (service == null) { return; } if (!mIsEnabled) { Looper myLooper = Looper.myLooper(); if (myLooper == Looper.getMainLooper()) { throw new IllegalStateException("Accessibility off. Did you forget to check that?"); } else { // If we're not running on the thread with the main looper, it's possible for // the state of accessibility to change between checking isEnabled and // calling this method. So just log the error rather than throwing the // exception. Log.e(LOG_TAG, "AccessibilityEvent sent with accessibility disabled"); return; } } userId = mUserId; } boolean doRecycle = false; try { event.setEventTime(SystemClock.uptimeMillis()); // it is possible that this manager is in the same process as the service but // client using it is called through Binder from another process. Example: MMS // app adds a SMS notification and the NotificationManagerService calls this method long identityToken = Binder.clearCallingIdentity(); // ！！！ doRecycle = service.sendAccessibilityEvent(event, userId); Binder.restoreCallingIdentity(identityToken); if (DEBUG) { Log.i(LOG_TAG, event + " sent"); } } catch (RemoteException re) { Log.e(LOG_TAG, "Error during sending " + event + " ", re); } finally { if (doRecycle) { event.recycle(); } } } private IAccessibilityManager getServiceLocked() { if (mService == null) { tryConnectToServiceLocked(null); } return mService; } private void tryConnectToServiceLocked(IAccessibilityManager service) { if (service == null) { IBinder iBinder = ServiceManager.getService(Context.ACCESSIBILITY_SERVICE); if (iBinder == null) { return; } service = IAccessibilityManager.Stub.asInterface(iBinder); } try { final int stateFlags = service.addClient(mClient, mUserId); setStateLocked(stateFlags); mService = service; } catch (RemoteException re) { Log.e(LOG_TAG, "AccessibilityManagerService is dead", re); } } </pre></td></tr></table></figure>

这里有使用到Android Binder机制，重点为IAccessibilityManager#sendAccessibilityEvent()方法，这里调用的是代理方法，实际代码逻辑在AccessibilityManagerService#sendAccessibilityEvent()： <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 </pre></td><td class="code"><pre>@Override public boolean sendAccessibilityEvent(AccessibilityEvent event, int userId) { synchronized(mLock) { // We treat calls from a profile as if made by its parent as profiles // share the accessibility state of the parent. The call below // performs the current profile parent resolution.. final int resolvedUserId = mSecurityPolicy.resolveCallingUserIdEnforcingPermissionsLocked(userId); // This method does nothing for a background user. if (resolvedUserId != mCurrentUserId) { return true; // yes, recycle the event } if (mSecurityPolicy.canDispatchAccessibilityEventLocked(event)) { mSecurityPolicy.updateActiveAndAccessibilityFocusedWindowLocked(event.getWindowId(), event.getSourceNodeId(), event.getEventType(), event.getAction()); mSecurityPolicy.updateEventSourceLocked(event); // ！！！ notifyAccessibilityServicesDelayedLocked(event, false); notifyAccessibilityServicesDelayedLocked(event, true); } if (mHasInputFilter && mInputFilter != null) { mMainHandler.obtainMessage(MainHandler.MSG_SEND_ACCESSIBILITY_EVENT_TO_INPUT_FILTER, AccessibilityEvent.obtain(event)).sendToTarget(); } event.recycle(); } return (OWN_PROCESS_ID != Binder.getCallingPid()); } private void notifyAccessibilityServicesDelayedLocked(AccessibilityEvent event, boolean isDefault) { try { UserState state = getCurrentUserStateLocked(); for (int i = 0, count = state.mBoundServices.size(); i < count; i++) { Service service = state.mBoundServices.get(i); if (service.mIsDefault == isDefault) { if (canDispatchEventToServiceLocked(service, event)) { service.notifyAccessibilityEvent(event); } } } } catch (IndexOutOfBoundsException oobe) { // An out of bounds exception can happen if services are going away // as the for loop is running. If that happens, just bail because // there are no more services to notify. } } </pre></td></tr></table></figure>

<ol>

<li>在方法中，最后会调用notifyAccessibilityServicesDelayedLocked()方法，然后将event进行回收；</li>

<li>在notifyAccessibilityServicesDelayedLocked()方法中，会获得所有Bound即绑定的Service，执行notifyAccessibilityEvent()方法，通过跟踪代码逻辑，最后会调用绑定Service的onAccessibilityEvent()方法。绑定的Service是指我们自己实现的继承于AccessibilityService的Service类，当你在设置-无障碍中开启服务之后即将服务绑定到AccessibilityManagerService中。</li>

</ol>

这样我们解决了第二个问题： AccessibilityService是如何做到监控捕捉用户行为的：（以点击事件为例） AccessibilityEvent产生： View#performClick()   -> View#sendAccessibilityEventUncheckedInternal()    -> ViewGroup#requestSendAccessibilityEvent()     -> ViewRootImpl#requestSendAccessibilityEvent()      -> AccessibilityManager#sendAccessibilityEvent(event)       -> AccessibilityManagerService#sendAccessibilityEvent()        -> AccessibilityManagerService#notifyAccessibilityServicesDelayedLocked()         -> Service#notifyAccessibilityEvent(event)

AccessibilityEvent处理： AccessibilityEvent   -> Binder驱动    -> IAccessibilityServiceClientWrapper#onAccessibilityEvent(AccessibilityEvent)     -> HandlerCaller#sendMessage(message); // message中包括AccessibilityEvent      -> IAccessibilityServiceClientWrapper#executeMessage();       -> Callbacks#onAccessibilityEvent(event);        -> AccessibilityService.this.onAccessibilityEvent(event);

<h6 id="AccessibilityService交互之查找控件"><a href="#AccessibilityService交互之查找控件" class="headerlink" title="AccessibilityService交互之查找控件"></a>AccessibilityService交互之查找控件</h6>在demo中，我们在MyAccessibilityService中调用了getRootInActiveWindow()方法获取被监控的View的所有结点，这些结点都封装成一个AccessibilityNodeInfo对象中。同时也调用AccessibilityNodeInfo#findAccessibilityNodeInfosByText()方法查找相应的控件。 这些方法的本质是调用了AccessibilityInteractionClient类的对应方法。 以AccessibilityInteractionClient#findAccessibilityNodeInfosByText()为例： <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 </pre></td><td class="code"><pre>public List<AccessibilityNodeInfo> findAccessibilityNodeInfosByText(int connectionId, int accessibilityWindowId, long accessibilityNodeId, String text) { try { IAccessibilityServiceConnection connection = getConnection(connectionId); if (connection != null) { final int interactionId = mInteractionIdCounter.getAndIncrement(); final long identityToken = Binder.clearCallingIdentity(); final boolean success = connection.findAccessibilityNodeInfosByText(accessibilityWindowId, accessibilityNodeId, text, interactionId, this, Thread.currentThread().getId()); Binder.restoreCallingIdentity(identityToken); if (success) { List<AccessibilityNodeInfo> infos = getFindAccessibilityNodeInfosResultAndClear(interactionId); if (infos != null) { finalizeAndCacheAccessibilityNodeInfos(infos, connectionId); return infos; } } } else { if (DEBUG) { Log.w(LOG_TAG, "No connection for connection id: " + connectionId); } } } catch (RemoteException re) { Log.w(LOG_TAG, "Error while calling remote" + " findAccessibilityNodeInfosByViewText", re); } return Collections.emptyList(); } </pre></td></tr></table></figure>

代码逻辑比较简单，就是直接调用IAccessibilityServiceConnection#findAccessibilityNodeInfosByText()方法。 IAccessibilityServiceConnection是一个aidl接口，从注释看，它是AccessibilitySerivce和AccessibilityManagerService之间沟通的桥梁。 猜想代码真正的实现在AccessibilityManagerService中。 AccessibilityManagerService.Service#findAccessibilityNodeInfosByText()： <figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 </pre></td><td class="code"><pre>@Override public boolean findAccessibilityNodeInfosByText(int accessibilityWindowId, long accessibilityNodeId, String text, int interactionId, IAccessibilityInteractionConnectionCallback callback, long interrogatingTid) throws RemoteException { final int resolvedWindowId; IAccessibilityInteractionConnection connection = null; Region partialInteractiveRegion = Region.obtain(); synchronized(mLock) { if (!isCalledForCurrentUserLocked()) { return false; } resolvedWindowId = resolveAccessibilityWindowIdLocked(accessibilityWindowId); final boolean permissionGranted = mSecurityPolicy.canGetAccessibilityNodeInfoLocked(this, resolvedWindowId); if (!permissionGranted) { return false; } else { connection = getConnectionLocked(resolvedWindowId); if (connection == null) { return false; } } if (!mSecurityPolicy.computePartialInteractiveRegionForWindowLocked(resolvedWindowId, partialInteractiveRegion)) { partialInteractiveRegion.recycle(); partialInteractiveRegion = null; } } final int interrogatingPid = Binder.getCallingPid(); final long identityToken = Binder.clearCallingIdentity(); MagnificationSpec spec = getCompatibleMagnificationSpecLocked(resolvedWindowId); try { connection.findAccessibilityNodeInfosByText(accessibilityNodeId, text, partialInteractiveRegion, interactionId, callback, mFetchFlags, interrogatingPid, interrogatingTid, spec); return true; } catch (RemoteException re) { if (DEBUG) { Slog.e(LOG_TAG, "Error calling findAccessibilityNodeInfosByText()"); } } finally { Binder.restoreCallingIdentity(identityToken); // Recycle if passed to another process. if (partialInteractiveRegion != null && Binder.isProxy(connection)) { partialInteractiveRegion.recycle(); } } return false; } </pre></td></tr></table></figure>

<ol>

<li>此方法在AccessibilityManagerService的内部类Service中实现，这个Service继承于IAccessibilityServiceConnection.Stub，验证了我上面的猜想是正确的；</li>

<li>代码重点是调用connection.findAccessibilityNodeInfosByText()，这里的connection实例与上面不同，它隶属于IAccessibilityInteractionConnection类。这个类同样是一个aidl接口，从注释上看，它又是AccessibilityManagerService与指定窗口的ViewRoot之间沟通的桥梁。 再次猜想，真正的代码逻辑在ViewRootImpl中。 查看ViewRootImpl.AccessibilityInteractionConnection#findAccessibilityNodeInfosByText()：

</li>

<li>同样的，此方法在ViewRootImpl的内部类AccessibilityInteractionConnection中实现，这个内部类继承于IAccessibilityServiceConnection.Stub，验证了我的猜想；

</li>

<li>查找控件等操作，ViewRootImpl并不是直接处理，而是交给AccessibilityInteractionController类去查找，查找到的结果会保存到一个callback中，这个callback为IAccessibilityInteractionConnectionCallback类型，它也是一个aidl接口，而AccessibilityInteractionClient类继承了IAccessibilityInteractionConnectionCallback.Stub，即最后查询后的结果会回调到AccessibilityInteractionClient类中，如上面AccessibilityInteractionClient#findAccessibilityNodeInfosByText()方法，最后会调用getFindAccessibilityNodeInfosResultAndClear()方法获取结果。具体如何寻找指定控件则不再分析代码。</li>

</ol>

<h6 id="AccessibilityService交互之执行控件操作"><a href="#AccessibilityService交互之执行控件操作" class="headerlink" title="AccessibilityService交互之执行控件操作"></a>AccessibilityService交互之执行控件操作</h6>类似的，与上面的流程基本相同，只是回调的时候，返回的是执行操作的返回值（True or False）。

到这里，我们解决了最后一个问题： AccessibilityService是如何做到查找控件，执行点击等操作的？ 总结： 寻找指定控件/执行操作   -> 交给AccessibilityInteractionClient类处理     -> Binder       -> AccessibilityManagerService类进行查找/执行操作         -> Binder           -> 指定窗口的ViewRoot（ViewRootImpl）进行查找/执行操作         <- Binder     <- 结果回调到AccessibilityInteractionClient类

<h4 id="四、有用代码记录"><a href="#四、有用代码记录" class="headerlink" title="四、有用代码记录"></a>四、有用代码记录</h4><ol>

<li>HandlerCaller类：结合Handler类和自定义的接口类（Caller.java），利用Handler的消息循环机制来分发消息，将最终的处理函数交给Caller#executeMessage()：

<figure class="highlight java"><table><tr><td class="gutter"><pre>1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 </pre></td><td class="code"><pre>// HandlerCaller.java public class HandlerCaller { final Looper mMainLooper; final Handler mH; final Callback mCallback; class MyHandler extends Handler { MyHandler(Looper looper, boolean async) { super(looper, null, async); } @Override public void handleMessage(Message msg) { mCallback.executeMessage(msg); } } public interface Callback { public void executeMessage(Message msg); } public HandlerCaller(Context context, Looper looper, Callback callback, boolean asyncHandler) { mMainLooper = looper != null ? looper : context.getMainLooper(); mH = new MyHandler(mMainLooper, asyncHandler); mCallback = callback; } public Handler getHandler() { return mH; } public void executeOrSendMessage(Message msg) { // If we are calling this from the main thread, then we can call // right through. Otherwise, we need to send the message to the // main thread. if (Looper.myLooper() == mMainLooper) { mCallback.executeMessage(msg); msg.recycle(); return; } mH.sendMessage(msg); } public void sendMessageDelayed(Message msg, long delayMillis) { mH.sendMessageDelayed(msg, delayMillis); } public boolean hasMessages(int what) { return mH.hasMessages(what); } public void removeMessages(int what) { mH.removeMessages(what); } public void removeMessages(int what, Object obj) { mH.removeMessages(what, obj); } public void sendMessage(Message msg) { mH.sendMessage(msg); } public SomeArgs sendMessageAndWait(Message msg) { if (Looper.myLooper() == mH.getLooper()) { throw new IllegalStateException("Can't wait on same thread as looper"); } SomeArgs args = (SomeArgs)msg.obj; args.mWaitState = SomeArgs.WAIT_WAITING; mH.sendMessage(msg); synchronized (args) { while (args.mWaitState == SomeArgs.WAIT_WAITING) { try { args.wait(); } catch (InterruptedException e) { return null; } } } args.mWaitState = SomeArgs.WAIT_NONE; return args; } public Message obtainMessage(int what) { return mH.obtainMessage(what); } // 省略部分代码 } </pre></td></tr></table></figure>

</li>

<li>HandlerCaller#sendMessageAndWait()：

</li>

</ol>

</div>

<a href="/tags/Android源码解析/" rel="tag"># Android源码解析</a>

</div>

EventBus 3.1.1 源码解析

</a>

</div>

易用版Popupwindow by Kotlin了解一下

</a>

</div>

</footer>

</div>

</article>

</div>

</div>

文章目录

</li>

站点概览

</li>

</ul>

Xu

Tencent / 一个自律的Developer

</div>

13

日志

</a>

</div>

1

分类

</a>

</div>

5

标签

</a>

</div>

</nav>

GitHub</a>

E-Mail</a>

掘金</a>

简书</a>

CSDN</a>

简历</a>

</div>

</section>

<div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-4"><a class="nav-link" href="#一、本文需要解决的问题">一、本文需要解决的问题</a></li><li class="nav-item nav-level-4"><a class="nav-link" href="#二、初步分析">二、初步分析</a><ol class="nav-child"><li class="nav-item nav-level-5"><a class="nav-link" href="#创建AccessibilityService">创建AccessibilityService</a></li><li class="nav-item nav-level-5"><a class="nav-link" href="#AccessibilityService配置">AccessibilityService配置</a></li><li class="nav-item nav-level-5"><a class="nav-link" href="#在manifest中进行注册">在manifest中进行注册</a></li><li class="nav-item nav-level-5"><a class="nav-link" href="#创建一个text为Test-的button控件，设置监听方法">创建一个text为Test!的button控件，设置监听方法</a></li><li class="nav-item nav-level-5"><a class="nav-link" href="#开启AccessibilityService">开启AccessibilityService</a></li><li class="nav-item nav-level-5"><a class="nav-link" href="#运行应用，点击text为Test-的按钮">运行应用，点击text为Test!的按钮</a></li></ol></li><li class="nav-item nav-level-4"><a class="nav-link" href="#三、源码解析">三、源码解析</a><ol class="nav-child"><li class="nav-item nav-level-6"><a class="nav-link" href="#AccessibilityService内部逻辑">AccessibilityService内部逻辑</a></li><li class="nav-item nav-level-6"><a class="nav-link" href="#AccessibilityService-java">AccessibilityService.java</a></li><li class="nav-item nav-level-6"><a class="nav-link" href="#IAccessibilityServiceClientWrapper">IAccessibilityServiceClientWrapper</a></li><li class="nav-item nav-level-6"><a class="nav-link" href="#AccessibilityService外部逻辑">AccessibilityService外部逻辑</a></li><li class="nav-item nav-level-6"><a class="nav-link" href="#AccessibilityService交互之查找控件">AccessibilityService交互之查找控件</a></li><li class="nav-item nav-level-6"><a class="nav-link" href="#AccessibilityService交互之执行控件操作">AccessibilityService交互之执行控件操作</a></li></ol></li></ol><li class="nav-item nav-level-4"><a class="nav-link" href="#四、有用代码记录">四、有用代码记录</a></li></div>

</div>

</section>

</div>

</aside>

</div>

</main>

Xu

</div>

</footer>

0%

</div>

if (Object.prototype.toString.call(window.Promise) !== '[object Function]') {

window.Promise = null;

}

</script>

function showTime(Counter) {

var query = new AV.Query(Counter);

var entries = [];

var $visitors = $(".leancloud_visitors");

$visitors.each(function () {

entries.push( $(this).attr("id").trim() );

});

query.containedIn('url', entries);

query.find()

.done(function (results) {

var COUNT_CONTAINER_REF = '.leancloud-visitors-count';

if (results.length === 0) {

$visitors.find(COUNT_CONTAINER_REF).text(0);

return;

}

for (var i = 0; i < results.length; i++) {

var item = results[i];

var url = item.get('url');

var time = item.get('time');

var element = document.getElementById(url);

$(element).find(COUNT_CONTAINER_REF).text(time);

}

for(var i = 0; i < entries.length; i++) {

var url = entries[i];

var element = document.getElementById(url);

var countSpan = $(element).find(COUNT_CONTAINER_REF);

if( countSpan.text() == '') {

countSpan.text(0);

}

})

.fail(function (object, error) {

console.log("Error: " + error.code + " " + error.message);

});

}

function addCount(Counter) {

var $visitors = $(".leancloud_visitors");

var url = $visitors.attr('id').trim();

var title = $visitors.attr('data-flag-title').trim();

var query = new AV.Query(Counter);

query.equalTo("url", url);

query.find({

success: function(results) {

if (results.length > 0) {

var counter = results[0];

counter.fetchWhenSave(true);

counter.increment("time");

counter.save(null, {

success: function(counter) {

var $element = $(document.getElementById(url));

$element.find('.leancloud-visitors-count').text(counter.get('time'));

error: function(counter, error) {

console.log('Failed to save Visitor num, with error message: ' + error.message);

}

});

} else {

var newcounter = new Counter();

/* Set ACL */

var acl = new AV.ACL();

acl.setPublicReadAccess(true);

acl.setPublicWriteAccess(true);

newcounter.setACL(acl);

/* End Set ACL */

newcounter.set("title", title);

newcounter.set("url", url);

newcounter.set("time", 1);

newcounter.save(null, {

success: function(newcounter) {

var $element = $(document.getElementById(url));

$element.find('.leancloud-visitors-count').text(newcounter.get('time'));

error: function(newcounter, error) {

console.log('Failed to create');

}

});

}

error: function(error) {

console.log('Error:' + error.code + " " + error.message);

}

});

}

$(function() {

var Counter = AV.Object.extend("Counter");

if ($('.leancloud_visitors').length == 1) {

addCount(Counter);

} else if ($('.post-title-link').length > 1) {

showTime(Counter);

}

});

</script>

(function(){

var bp = document.createElement('script');

var curProtocol = window.location.protocol.split(':')[0];

if (curProtocol === 'https') {

bp.src = 'https://zz.bdstatic.com/linksubmit/push.js';

View remainder of file in raw view

FilesExpand file tree

3435cf36.html

Latest commit

History

3435cf36.html

File metadata and controls