Android 双屏异显自适应Dialog的实现，
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Android 双屏异显自适应Dialog的实现，
目录
- 一、前言
- 需求
- 问题
- 二、方案
- 方案：自定义Presentation
- 原理
- WindowType问题解决
- WindowManagerImpl 问题
- 方案：Delagate方式：
- 兼容
- 总结
一、前言
Android 多屏互联的时代，必然会出现多屏连接的问题，通常意义上的多屏连接包括HDMI/USB、WifiDisplay，除此之外Android 还有OverlayDisplay和VirtualDisplay，其中VirtualDisplay相比不少人录屏的时候都会用到，在Android中他们都是Display，除了物理屏幕，你在OverlayDisplay和VirtualDisplay同样也可以展示弹窗或者展示Activity，所有的Display的差异化通过DisplayManagerService 进行了兼容，同样任意一种Display都拥有自己的密度和大小以及display Id，对于测试双屏应用，一般也可以通过VirtualDisplay进行模拟操作。
需求
本篇主要解决副屏Dialog 组建展示问题。存在任意类型的副屏时，让 Dialog 展示在副屏上，如果不存在，就需要让它自动展示在主屏上。
为什么会有这种需求呢？默认情况下，实现双屏异显的时候， 通常不是使用Presentation就是Activity，然而，Dialog只能展示在主屏上，而Presentation只能展示的副屏上。想象一下这种双屏场景，在切换视频的时候，Loading展示应该是在主屏还是副屏呢 ？毫无疑问，答案当然是副屏。
问题
我们要解决的问题当然是随着场景的切换，Dialog展示在不同的屏幕上。同样，内容也可以这样展示，当存在副屏的时候在副屏上展示内容，当只有主屏的时候在主屏上展示内容。
二、方案
我们这里梳理一下两种方案。
方案：自定义Presentation
作为Presentation的核心点有两个，其中一个是displayId，另一个是WindowType，第一个是通常意义上指定Display Id，第二个是窗口类型。如果是副屏，那么displayId是必须的参数，且不能和DefaultDisplay的id一样，除此之外WindowType是一个需要重点关注的东西。
早期的 TYPE_PRESENTATION 存在指纹信息 “被借用” 而造成用户资产损失的风险，即便外部无法获取，但是早期的Android 8.0版本利用 （TYPE_PRESENTATION=TYPE_APPLICATION_OVERLAY-1）可以实现屏幕外弹框，在之后的版本做了修复，同时对 TYPE_PRESENTATION 展示必须有 Token 等校验，但是在这种过程中，Presentation的WindowType 变了又变，因此，我们如何获取到兼容每个版本的WindowType呢？
原理
Display Id的问题我们不需要重点处理，从display 获取即可。WindowType才是重点，方法当然是有的，我们不继承Presentation，而是继承Dialog因此自行实现可以参考 Presentation 中的代码，当然难点是 WindowManagerImpl 和WindowType类获取，前者 @hide 标注的，而后者不固定。
早期我们可以利用 compileOnly layoutlib.jar 的方式导入 WindowManagerImpl，但是新版本中 layoutlib.jar 中的类已经几乎被删，另外如果要使用 layoutlib.jar，那么你的项目中的 kotlin 版本就会和 layoutlib.jar 产生冲突，虽然可以删除相关的类，但是这种维护方式非常繁琐，因此我们这里借助反射实现。当然除了反射也可以利用Dexmaker或者xposed Hook方式，只是复杂性会很多。
WindowType问题解决
我们知道，创建Presentation的时候，framework源码是设置了WindowType的，我们完全在我们自己的Dialog创建Presentation对象，读取出来设置上到我们自己的Dialog上即可。
不过，我们先要对Display进行隔离，避免主屏走这段逻辑
WindowManager wm = (WindowManager) outerContext.getSystemService(WINDOW_SERVICE);
if(display==null || wm.getDefaultDisplay().getDisplayId()==display.getDisplayId()){
return;
}
//注意，这里需要借助Presentation的一些属性，否则无法正常弹出弹框，要么有权限问题、要么有token问题
Presentation presentation = new Presentation(outerContext, display, theme); WindowManager.LayoutParams standardAttributes =presentation.getWindow().getAttributes(); final Window w = getWindow(); final WindowManager.LayoutParams attr = w.getAttributes(); attr.token = standardAttributes.token; w.setAttributes(attr); //type 源码中是TYPE_PRESENTATION，事实上每个版本是不一样的，因此这里动态获取 w.setGravity(Gravity.FILL); w.setType(standardAttributes.type);
WindowManagerImpl 问题
其实我们知道，Presentation的WindowManagerImpl并不是给自己用的，而是给Dialog上的其他组件（如Menu、PopWindow等），将其他组件加到Dialog的 Window上，因为在Android系统中，WindowManager都是parent Window所具备的能力，所以创建这个不是为了把Dialog加进去，而是为了把基于Dialog的Window组件加到Dialog上，这和Activity是一样的。那么，其实如果我们没有Menu、PopWindow，这里实际上是可以不处理的，但是作为一个完整的类，我们这里使用反射处理一下。
怎么处理呢？
我们知道，异显屏的Context是通过createDisplayContext创建的，但是我们这里并不是Hook这个方法，只是在创建这个Display Context之后，再通过ContextThemeWrapper，设置进去即可。
private static Context createPresentationContext(
Context outerContext, Display display, int theme) {
if (outerContext == null) {
throw new IllegalArgumentException("outerContext must not be null");
}
WindowManager outerWindowManager = (WindowManager) outerContext.getSystemService(WINDOW_SERVICE);
if (display == null || display.getDisplayId()==outerWindowManager.getDefaultDisplay().getDisplayId()) {
return outerContext;
}
Context displayContext = outerContext.createDisplayContext(display);
if (theme == 0) {
TypedValue outValue = new TypedValue();
displayContext.getTheme().resolveAttribute(
android.R.attr.presentationTheme, outValue, true);
theme = outValue.resourceId;
}
// Derive the display's window manager from the outer window manager.
// We do this because the outer window manager have some extra information
// such as the parent window, which is important if the presentation uses
// an application window type.
// final WindowManager outerWindowManager =
// (WindowManager) outerContext.getSystemService(WINDOW_SERVICE);
// final WindowManagerImpl displayWindowManager =
// outerWindowManager.createPresentationWindowManager(displayContext);
WindowManager displayWindowManager = null;
try {
ClassLoader classLoader = ComplexPresentationV1.class.getClassLoader();
Class<?> loadClass = classLoader.loadClass("android.view.WindowManagerImpl");
Method createPresentationWindowManager = loadClass.getDeclaredMethod("createPresentationWindowManager", Context.class);
displayWindowManager = (WindowManager) loadClass.cast(createPresentationWindowManager.invoke(outerWindowManager,displayContext));
} catch (ClassNotFoundException | NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
final WindowManager windowManager = displayWindowManager;
return new ContextThemeWrapper(displayContext, theme) {
@Override
public Object getSystemService(String name) {
if (WINDOW_SERVICE.equals(name)) {
return windowManager;
}
return super.getSystemService(name);
}
};
}
全部源码
public class ComplexPresentationV1 extends Dialog {
private static final String TAG = "ComplexPresentationV1";
private static final int MSG_CANCEL = 1;
private Display mPresentationDisplay;
private DisplayManager mDisplayManager;
/**
* Creates a new presentation that is attached to the specified display
* using the default theme.
*
* @param outerContext The context of the application that is showing the presentation.
* The presentation will create its own context (see {@link #getContext()}) based
* on this context and information about the associated display.
* @param display The display to which the presentation should be attached.
*/
public ComplexPresentationV1(Context outerContext, Display display) {
this(outerContext, display, 0);
}
/**
* Creates a new presentation that is attached to the specified display
* using the optionally specified theme.
*
* @param outerContext The context of the application that is showing the presentation.
* The presentation will create its own context (see {@link #getContext()}) based
* on this context and information about the associated display.
* @param display The display to which the presentation should be attached.
* @param theme A style resource describing the theme to use for the window.
* See <a href="{@docRoot}guide/topics/resources/available-resources.html#stylesandthemes">
* Style and Theme Resources</a> for more information about defining and using
* styles. This theme is applied on top of the current theme in
* <var>outerContext</var>. If 0, the default presentation theme will be used.
*/
public ComplexPresentationV1(Context outerContext, Display display, int theme) {
super(createPresentationContext(outerContext, display, theme), theme);
WindowManager wm = (WindowManager) outerContext.getSystemService(WINDOW_SERVICE);
if(display==null || wm.getDefaultDisplay().getDisplayId()==display.getDisplayId()){
return;
}
mPresentationDisplay = display;
mDisplayManager = (DisplayManager)getContext().getSystemService(DISPLAY_SERVICE);
//注意，这里需要借助Presentation的一些属性，否则无法正常弹出弹框，要么有权限问题、要么有token问题
Presentation presentation = new Presentation(outerContext, display, theme);
WindowManager.LayoutParams standardAttributes = presentation.getWindow().getAttributes();
final Window w = getWindow();
final WindowManager.LayoutParams attr = w.getAttributes();
attr.token = standardAttributes.token;
w.setAttributes(attr);
w.setType(standardAttributes.type);
//type 源码中是TYPE_PRESENTATION，事实上每个版本是不一样的，因此这里动态获取
w.setGravity(Gravity.FILL);
setCanceledOnTouchOutside(false);
}
/**
* Gets the {@link Display} that this presentation appears on.
*
* @return The display.
*/
public Display getDisplay() {
return mPresentationDisplay;
}
/**
* Gets the {@link Resources} that should be used to inflate the layout of this presentation.
* This resources object has been configured according to the metrics of the
* display that the presentation appears on.
*
* @return The presentation resources object.
*/
public Resources getResources() {
return getContext().getResources();
}
@Override
protected void onStart() {
super.onStart();
if(mPresentationDisplay ==null){
return;
}
mDisplayManager.registerDisplayListener(mDisplayListener, mHandler);
// Since we were not watching for display changes until just now, there is a
// chance that the display metrics have changed. If so, we will need to
// dismiss the presentation immediately. This case is expected
// to be rare but surprising, so we'll write a log message about it.
if (!isConfigurationStillValid()) {
Log.i(TAG, "Presentation is being dismissed because the "
+ "display metrics have changed since it was created.");
mHandler.sendEmptyMessage(MSG_CANCEL);
}
}
@Override
protected void onStop() {
if(mPresentationDisplay ==null){
return;
}
mDisplayManager.unregisterDisplayListener(mDisplayListener);
super.onStop();
}
/**
* Inherited from {@link Dialog#show}. Will throw
* {@link android.view.WindowManager.InvalidDisplayException} if the specified secondary
* {@link Display} can't be found.
*/
@Override
public void show() {
super.show();
}
/**
* Called by the system when the {@link Display} to which the presentation
* is attached has been removed.
*
* The system automatically calls {@link #cancel} to dismiss the presentation
* after sending this event.
*
* @see #getDisplay
*/
public void onDisplayRemoved() {
}
/**
* Called by the system when the properties of the {@link Display} to which
* the presentation is attached have changed.
*
* If the display metrics have changed (for example, if the display has been
* resized or rotated), then the system automatically calls
* {@link #cancel} to dismiss the presentation.
*
* @see #getDisplay
*/
public void onDisplayChanged() {
}
private void handleDisplayRemoved() {
onDisplayRemoved();
cancel();
}
private void handleDisplayChanged() {
onDisplayChanged();
// We currently do not support configuration changes for presentations
// (although we could add that feature with a bit more work).
// If the display metrics have changed in any way then the current configuration
// is invalid and the application must recreate the presentation to get
// a new context.
if (!isConfigurationStillValid()) {
Log.i(TAG, "Presentation is being dismissed because the "
+ "display metrics have changed since it was created.");
cancel();
}
}
private boolean isConfigurationStillValid() {
if(mPresentationDisplay ==null){
return true;
}
DisplayMetrics dm = new DisplayMetrics();
mPresentationDisplay.getMetrics(dm);
try {
Method equalsPhysical = DisplayMetrics.class.getDeclaredMethod("equalsPhysical", DisplayMetrics.class);
return (boolean) equalsPhysical.invoke(dm,getResources().getDisplayMetrics());
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
return false;
}
private static Context createPresentationContext(
Context outerContext, Display display, int theme) {
if (outerContext == null) {
throw new IllegalArgumentException("outerContext must not be null");
}
WindowManager outerWindowManager = (WindowManager) outerContext.getSystemService(WINDOW_SERVICE);
if (display == null || display.getDisplayId()==outerWindowManager.getDefaultDisplay().getDisplayId()) {
return outerContext;
}
Context displayContext = outerContext.createDisplayContext(display);
if (theme == 0) {
TypedValue outValue = new TypedValue();
displayContext.getTheme().resolveAttribute(
android.R.attr.presentationTheme, outValue, true);
theme = outValue.resourceId;
}
// Derive the display's window manager from the outer window manager.
// We do this because the outer window manager have some extra information
// such as the parent window, which is important if the presentation uses
// an application window type.
// final WindowManager outerWindowManager =
// (WindowManager) outerContext.getSystemService(WINDOW_SERVICE);
// final WindowManagerImpl displayWindowManager =
// outerWindowManager.createPresentationWindowManager(displayContext);
WindowManager displayWindowManager = null;
try {
ClassLoader classLoader = ComplexPresentationV1.class.getClassLoader();
Class<?> loadClass = classLoader.loadClass("android.view.WindowManagerImpl");
Method createPresentationWindowManager = loadClass.getDeclaredMethod("createPresentationWindowManager", Context.class);
displayWindowManager = (WindowManager) loadClass.cast(createPresentationWindowManager.invoke(outerWindowManager,displayContext));
} catch (ClassNotFoundException | NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
final WindowManager windowManager = displayWindowManager;
return new ContextThemeWrapper(displayContext, theme) {
@Override
public Object getSystemService(String name) {
if (WINDOW_SERVICE.equals(name)) {
return windowManager;
}
return super.getSystemService(name);
}
};
}
private final DisplayManager.DisplayListener mDisplayListener = new DisplayManager.DisplayListener() {
@Override
public void onDisplayAdded(int displayId) {
}
@Override
public void onDisplayRemoved(int displayId) {
if (displayId == mPresentationDisplay.getDisplayId()) {
handleDisplayRemoved();
}
}
@Override
public void onDisplayChanged(int displayId) {
if (displayId == mPresentationDisplay.getDisplayId()) {
handleDisplayChanged();
}
}
};
private final Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_CANCEL:
cancel();
break;
}
}
};
}
方案：Delagate方式：
第一种方案利用反射，但是android 9 开始，很多 @hide 反射不被允许，但是办法也是很多的，比如 freeflection 开源项目，不过对于开发者，能减少对@hide的使用也是为了后续的维护。此外还有一个需要注意的是 Presentation 继承的是 Dialog 构造方法是无法被包外的子类使用，但是影响不大，我们在和Presentation的包名下创建我们的自己的Dialog依然可以解决。不过，对于反射天然厌恶的人来说，可以使用代理。
这种方式借壳 Dialog，套用 Dialog 一层，以代理方式实现，不过相比前一种方案来说，这种方案也有很多缺陷，比如他的onCreate\onShow\onStop\onAttachToWindow\onDetatchFromWindow等方法并没有完全和Dialog同步，需要做下兼容。
兼容
onAttachToWindow\onDetatchFromWindow
WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
if (display != null && display.getDisplayId() != wm.getDefaultDisplay().getDisplayId()) {
dialog = new Presentation(context, display, themeResId);
} else {
dialog = new Dialog(context, themeResId);
}
//下面兼容attach和detatch问题
mDecorView = dialog.getWindow().getDecorView();
mDecorView.addOnAttachStateChangeListener(this);
onShow和\onStop
@Override
public void show() {
if (!isCreate) {
onCreate(null);
isCreate = true;
}
dialog.show();
if (!isStart) {
onStart();
isStart = true;
}
}
@Override
public void dismiss() {
dialog.dismiss();
if (isStart) {
onStop();
isStart = false;
}
}
从兼容代码上来看，显然没有做到Dialog那种同步，因此只适合在单一线程中使用。
总结
本篇总结了2种异显屏弹窗，总体上来说，都有一定的瑕疵，但是第一种方案显然要好的多，主要是View更新上和可扩展上，当然第二种对于非多线程且不关注严格回调的需求，也是足以应付，在实际情况中，合适的才是最重要的。
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