Android弹窗组件工作机制之Dialog、DialogFragment(二)

二、Dialog的消失

1、dismiss

private final Runnable mDismissAction = this::dismissDialog;public void dismiss() {if (Looper.myLooper() == mHandler.getLooper()) {dismissDialog();} else {mHandler.post(mDismissAction);}
}
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保证UI操作都在主线程执行，而且引用了Java8新特性写法this::dismissDialog，最后都会调用dismissDialog()

2、dismissDialog

void dismissDialog() {if (mDecor == null || !mShowing) {return;}if (mWindow.isDestroyed()) {Log.e(TAG, "Tried to dismissDialog() but the Dialog's window was already destroyed!");return;}try {//这里移除DecorViewmWindowManager.removeViewImmediate(mDecor);} finally {if (mActionMode != null) {mActionMode.finish();}mDecor = null;mWindow.closeAllPanels();onStop();mShowing = false;sendDismissMessage();}
}
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从show中知道，我们将DecorView加入到WindowManager中去，所以这里移除的是DecorView

3、WindowManagerImpl.removeViewImmediate

public void removeViewImmediate(View view) {//委托给mGlobal来进行实现mGlobal.removeView(view, true);
}
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同样的交给WindowManagerGlobal去处理

4、WindowManagerGlobal.removeView

public void removeView(View view, boolean immediate) {if (view == null) {throw new IllegalArgumentException("view must not be null");}synchronized (mLock) {//待remove view的索引int index = findViewLocked(view, true);//mRoots保存着每一个viewRootImpl对象View curView = mRoots.get(index).getView();//真正对view进行了remove操作removeViewLocked(index, immediate);if (curView == view) {return;}throw new IllegalStateException("Calling with view " + view+ " but the ViewAncestor is attached to " + curView);}
}
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找到对应要移除的View后进行View逻辑处理工作

5、WindowManagerGlobal.removeViewLocked

private void removeViewLocked(int index, boolean immediate) {ViewRootImpl root = mRoots.get(index);View view = root.getView();if (view != null) {InputMethodManager imm = InputMethodManager.getInstance();if (imm != null) {imm.windowDismissed(mViews.get(index).getWindowToken());}}//重点在ViewRootImpl中的die方法中boolean deferred = root.die(immediate);if (view != null) {view.assignParent(null);if (deferred) {mDyingViews.add(view);}}
}
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找到对应的ViewRootImpl，进行移除并释放工作

6、ViewRootImpl.die

boolean die(boolean immediate) {if (immediate && !mIsInTraversal) {//继续跟踪doDie();return false;}if (!mIsDrawing) {destroyHardwareRenderer();} else {Log.e(TAG, "Attempting to destroy the window while drawing!\n" +"  window=" + this + ", title=" + mWindowAttributes.getTitle());}mHandler.sendEmptyMessage(MSG_DIE);return true;
}
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7、ViewRootImpl.doDie

void doDie() {checkThread();if (LOCAL_LOGV) Log.v(TAG, "DIE in " + this + " of " + mSurface);synchronized (this) {if (mRemoved) {return;}mRemoved = true;if (mAdded) {//这里是真正移除Dialog的ViewdispatchDetachedFromWindow();}if (mAdded && !mFirst) {//硬件渲染destroydestroyHardwareRenderer();if (mView != null) {int viewVisibility = mView.getVisibility();boolean viewVisibilityChanged = mViewVisibility != viewVisibility;if (mWindowAttributesChanged || viewVisibilityChanged) {// If layout params have been changed, first give them// to the window manager to make sure it has the correct// animation info.try {if ((relayoutWindow(mWindowAttributes, viewVisibility, false)& WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) {mWindowSession.finishDrawing(mWindow);}} catch (RemoteException e) {}}//Surface的释放mSurface.release();}}mAdded = false;}//移除之前存储的变量WindowManagerGlobal.getInstance().doRemoveView(this);
}
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保证线程安全后，做移除和释放工作

8、WindowManagerGlobal.doRemoveView

一般程序最后的工作都是释放工作，移除之前存储的变量

void doRemoveView(ViewRootImpl root) {synchronized (mLock) {final int index = mRoots.indexOf(root);if (index >= 0) {//释放工作mRoots.remove(index);mParams.remove(index);final View view = mViews.remove(index);mDyingViews.remove(view);}}if (HardwareRenderer.sTrimForeground && HardwareRenderer.isAvailable()) {doTrimForeground();}
}
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9、ViewRootImpl.dispatchDetachedFromWindow

void dispatchDetachedFromWindow() {if (mView != null && mView.mAttachInfo != null) {mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(false);//此方法会回调onDetachedFromWindow方法，会做资源的回收mView.dispatchDetachedFromWindow();}mAccessibilityInteractionConnectionManager.ensureNoConnection();mAccessibilityManager.removeAccessibilityStateChangeListener(mAccessibilityInteractionConnectionManager);mAccessibilityManager.removeHighTextContrastStateChangeListener(mHighContrastTextManager);removeSendWindowContentChangedCallback();destroyHardwareRenderer();setAccessibilityFocus(null, null);mView.assignParent(null);mView = null;mAttachInfo.mRootView = null;mSurface.release();if (mInputQueueCallback != null && mInputQueue != null) {mInputQueueCallback.onInputQueueDestroyed(mInputQueue);mInputQueue.dispose();mInputQueueCallback = null;mInputQueue = null;}if (mInputEventReceiver != null) {mInputEventReceiver.dispose();mInputEventReceiver = null;}try {//这里调用了mWindowSession的remove方法，在WindowManagerService层通过IPC机制完成真正的window删除mWindowSession.remove(mWindow);} catch (RemoteException e) {}// Dispose the input channel after removing the window so the Window Manager// doesn't interpret the input channel being closed as an abnormal termination.if (mInputChannel != null) {mInputChannel.dispose();mInputChannel = null;}mDisplayManager.unregisterDisplayListener(mDisplayListener);unscheduleTraversals();
}
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到最后会和添加View的时候完成闭环，还是通过WindowSession的IPC机制去调用的，最后在WindowManagerService层通过IPC机制去实现的 ##总结 1.Dialog的dismiss和show形成闭环，调用的过程是相似的，只不过多了资源的释放环节

DialogFragment

DialogFragment本身继承自Fragment

public class DialogFragment extends Fragmentimplements DialogInterface.OnCancelListener, DialogInterface.OnDismissListener
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在平时中，我们需要自定义WeDialogFragment，而且在正式开发中踩过的坑：

需要对参数进行onSaveInstanceState操作，这类操作主要是防止异步吊起DialogFragment报nullPoint的Bug
需要重写show()，对show做一层弹出时候的保护，这类操作主要是防止异步吊起DialogFragment报onSaveInstanceState的Bug

public class WeDialogFragment extends DialogFragment {@Overridepublic void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);Bundle bundle = new Bundle();bundle.putString(BUNDLE_TITLE, title);}@Overridepublic void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);setStyle(DialogFragment.STYLE_NO_TITLE, R.style.WeDialog);if (savedInstanceState != null) {title = savedInstanceState.getString(BUNDLE_TITLE);}}@Overridepublic Dialog onCreateDialog(Bundle savedInstanceState) {Dialog dialog = super.onCreateDialog(savedInstanceState);dialog.setCanceledOnTouchOutside(true);dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);dialog.getWindow().setWindowAnimations(R.style.DialogAnimation);dialog.getWindow().setBackgroundDrawableResource(android.R.color.transparent);return dialog;}@Nullable@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {return inflater.inflate(R.layout.view_fragment_dialog, container, false);}@Overridepublic void show(FragmentManager manager, String tag) {if (!manager.isStateSaved()) {super.show(manager, tag);}}
}
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然后在Activity中弹出DialogFragment

WeDialogFragment weDialogFragment = new WeDialogFragment();
weDialogFragment.show(activity.getSupportFragmentManager(),"weDialogFragment");
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一、DialogFragment的显示

1、DialogFragment.show

public void show(FragmentManager manager, String tag) {mDismissed = false;mShownByMe = true;FragmentTransaction ft = manager.beginTransaction();ft.add(this, tag);ft.commit();
}
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show的方法其实就是对Fragment的处理，将Fragment添加到Fragment栈中

二、DialogFragment的隐藏

####1、DialogFragment.dismiss

public void dismiss() {dismissInternal(false);
}public void dismissAllowingStateLoss() {dismissInternal(true);
}void dismissInternal(boolean allowStateLoss) {if (mDismissed) {return;}mDismissed = true;mShownByMe = false;if (mDialog != null) {mDialog.dismiss();}mViewDestroyed = true;if (mBackStackId >= 0) {getFragmentManager().popBackStack(mBackStackId,FragmentManager.POP_BACK_STACK_INCLUSIVE);mBackStackId = -1;} else {FragmentTransaction ft = getFragmentManager().beginTransaction();ft.remove(this);if (allowStateLoss) {ft.commitAllowingStateLoss();} else {ft.commit();}}
}
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dismiss的方法也是对Fragment的处理，将Fragment移除到Fragment栈中

三、Dialog的创建

1、DialogFragment.onCreateDialog

@NonNull
public Dialog onCreateDialog(Bundle savedInstanceState) {return new Dialog(getActivity(), getTheme());
}
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和创建普通的Dialog没什么区别，我们重写该方法，可以自定义弹出AlertDialog等其他自定义Dialog

四、Dialog的视图

1、DialogFragment.onActivityCreated

@Override
public void onActivityCreated(Bundle savedInstanceState) {super.onActivityCreated(savedInstanceState);if (!mShowsDialog) {return;}//拿到的就是onCreateView返回值的view对象，具体可以在Fragment源码找到View view = getView();if (view != null) {if (view.getParent() != null) {throw new IllegalStateException("DialogFragment can not be attached to a container view");}//真正设置viewmDialog.setContentView(view);}final Activity activity = getActivity();if (activity != null) {mDialog.setOwnerActivity(activity);}mDialog.setCancelable(mCancelable);mDialog.setOnCancelListener(this);mDialog.setOnDismissListener(this);if (savedInstanceState != null) {Bundle dialogState = savedInstanceState.getBundle(SAVED_DIALOG_STATE_TAG);if (dialogState != null) {mDialog.onRestoreInstanceState(dialogState);}}
}
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在Activity创建的时候，Fragment的周期会回调onActivityCreated，从而对Dialog设置视图

五、Dialog的显示隐藏

Dialog显示隐藏就简单了，随着Fragment的生命周期显示和隐藏，直接看代码就行了

@Override
public void onStart() {super.onStart();if (mDialog != null) {mViewDestroyed = false;mDialog.show();}
}@Override
public void onStop() {super.onStop();if (mDialog != null) {mDialog.hide();}
}
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总结

DialogFragment = Fragment + Dialog，DialogFragment本身继承Fragment，Fragment只是用来依附在Activity上，可以监听Activity的生命周期，从而去通知Dialog做对应的操作，而Dialog才是我们正在显示在屏幕上的弹窗，而非一个Fragment。这里的Dialog真正显示出来的View是从**onCreateView()中获取view后，在源码中调用dialog的setContentView()**显示出来的

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