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使用
效果预览
Demo结构
一个Activity、一个Service和两个布局文件。布局十分简单，这里就不贴了，大概描述下。activity_main.xml中俩按钮，layout_window.xml中一个TextView。ok，首先看下MainActivity。MainActivity中只有俩按钮，点击启动WindowService，点击停止WindowService。没啥好说的。直接看WindowService。
/** * @author CSDN 一口仨馍 */
public class WindowService extends Service {
private final String TAG = this.getClass().getSimpleName();
private WindowManager.LayoutParams wmParams;
private WindowManager mWindowManager;
private View mWindowView;
private TextView mPercentTv;
private int mStartX;
private int mStartY;
private int mEndX;
private int mEndY;
@Override
public void onCreate() {
super.onCreate();
Log.i(TAG, "onCreate");
initWindowParams();
initView();
addWindowView2Window();
initClick();
}
private void initWindowParams() {
mWindowManager = (WindowManager) getApplication().getSystemService(getApplication().WINDOW_SERVICE);
wmParams = new WindowManager.LayoutParams();
// 更多type：https://developer.android.com/reference/android/view/WindowManager.LayoutParams.html#TYPE_PHONE
wmParams.type = WindowManager.LayoutParams.TYPE_PHONE;
wmParams.format = PixelFormat.TRANSLUCENT;
// 更多falgs:https://developer.android.com/reference/android/view/WindowManager.LayoutParams.html#FLAG_NOT_FOCUSABLE
wmParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
wmParams.gravity = Gravity.LEFT | Gravity.TOP;
wmParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
wmParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
}
private void initView() {
mWindowView = LayoutInflater.from(getApplication()).inflate(R.layout.layout_window, null);
mPercentTv = (TextView) mWindowView.findViewById(R.id.percentTv);
}
private void addWindowView2Window() {
mWindowManager.addView(mWindowView, wmParams);
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
Log.i(TAG, "onStartCommand");
return super.onStartCommand(intent, flags, startId);
}
@Override
public void onDestroy() {
super.onDestroy();
if (mWindowView != null) {
//移除悬浮窗口
Log.i(TAG, "removeView");
mWindowManager.removeView(mWindowView);
}
Log.i(TAG, "onDestroy");
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
}在设置各种属性之后，直接向WindowManager中添加mWindowView（也就是我们自己的布局layout_window.xml）。在此之前需要在AndroidManifest。xml中注册Service和添加相应的限权。
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
<uses-permission android:name="android.permission.GET_TASKS" />
<service android:name=".WindowService"/>现在点击startBtn，桌面上已经可以出现悬浮窗。但是没有拖动啦点击啦这些动作。小意思，重写点击事件。根据拖动距离，判断是点击还是滑动。由于onTouchEvent()的优先级比onClick高，拖动时在需要的拦截的地方，return true就ok了。具体如下：
private void initClick() {
mPercentTv.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mStartX = (int) event.getRawX();
mStartY = (int) event.getRawY();
break;
case MotionEvent.ACTION_MOVE:
mEndX = (int) event.getRawX();
mEndY = (int) event.getRawY();
if (needIntercept()) {
//getRawX是触摸位置相对于屏幕的坐标，getX是相对于按钮的坐标
wmParams.x = (int) event.getRawX() - mWindowView.getMeasuredWidth() / 2;
wmParams.y = (int) event.getRawY() - mWindowView.getMeasuredHeight() / 2;
mWindowManager.updateViewLayout(mWindowView, wmParams);
return true;
}
break;
case MotionEvent.ACTION_UP:
if (needIntercept()) {
return true;
}
break;
default:
break;
}
return false;
}
});
mPercentTv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (isAppAtBackground(WindowService.this)) {
Intent intent = new Intent(WindowService.this, MainActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
}
}
});
}
/** * 是否拦截 * @return true:拦截;false:不拦截. */
private boolean needIntercept() {
if (Math.abs(mStartX - mEndX) > 30 || Math.abs(mStartY - mEndY) > 30) {
return true;
}
return false;
}这里在onClick中进行了一个程序前后台的判断操作，方法如下：
/** *判断当前应用程序处于前台还是后台 */
private boolean isAppAtBackground(final Context context) {
ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
List<ActivityManager.RunningTaskInfo> tasks = am.getRunningTasks(1);
if (!tasks.isEmpty()) {
ComponentName topActivity = tasks.get(0).topActivity;
if (!topActivity.getPackageName().equals(context.getPackageName())) {
return true;
}
}
return false;
}至此为止。悬浮窗已经显示出来，点击拖动事件也已经搞定。虽然和360悬浮窗差距还蛮大，但是剩下的只剩具体实现。像addView()，removeView()和动画等等，这里就不再具体实现。本着知其然知其所以然的精神，下文是整个流程的源码解析。
源码解析
初始化解析
在WindowService中通过getApplication().getSystemService(getApplication().WINDOW_SERVICE)获取到一个WindowManager，姑且称这么过程为初始化。
源码位置：frameworks/base/core/java/Android/app/Service.java
Service#getApplication()
public final Application getApplication() {
return mApplication;
}首先获取应用程序的Application对象，然后调用Application#getSystemService()。但是，在Application中并没有getSystemService()这个方法，那么这个方法肯定在父类中或在某个接口中。追踪发现在其父类ContextWrapper中。跟进。
源码位置：frameworks/base/core/java/Android/content/ContextWrapper.java
ContextWrapper#getSystemServiceName()
@Override
public String getSystemServiceName(Class<?> serviceClass) {
return mBase.getSystemServiceName(serviceClass);
}成员变量mBase为Context对象，跟进。
源码位置：frameworks/base/core/java/Android/content/Context.java
Context#getSystemServiceName()
public final <T> T getSystemService(Class<T> serviceClass) {
String serviceName = getSystemServiceName(serviceClass);
return serviceName != null ? (T)getSystemService(serviceName) : null;
}
public abstract Object getSystemService(@ServiceName @NonNull String name);Context的实现类是ContextImpl，接下来获取服务的方式和Android XML布局文件解析过程源码解析中一样，为了节省篇幅，直接进入到SystemServiceRegistry中的静态代码快
源码位置：frameworks/base/core/java/android/app/SystemServiceRegistry.java
static {
...
registerService(Context.WINDOW_SERVICE, WindowManager.class,
new CachedServiceFetcher<WindowManager>() {
@Override
public WindowManager createService(ContextImpl ctx) {
return new WindowManagerImpl(ctx.getDisplay());
}});
...
}这里返回了WindowManagerImpl对象，不过最后强转称了父类WindowManager。目前为止，已经获取到了WindowManager对象，各种参数也已经初始化完成。接下来只有一行WindowManager.addView()。真可谓简单到极致。极度的简单往往是繁琐的假象。接下来，才是本文真正的开始。
WindowManager.addView()解析
源码位置：frameworks/base/core/Java/Android/view/WindowManagerImpl.java
WindowManagerImpl#addView()
@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
applyDefaultToken(params);
mGlobal.addView(view, params, mDisplay, mParentWindow);
}首先验证Token，这里不作为重点。接下来还有个addView()跟进。
源码位置：frameworks/base/core/Java/Android/view/WindowManagerGlobal.java
WindowManagerGlobal#addView()
public void addView(View view, ViewGroup.LayoutParams params,
Display display, Window parentWindow) {
// 参数效验
...
ViewRootImpl root;
synchronized (mLock) {
// 查找缓存，类型效验
...
root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
mViews.add(view);
mRoots.add(root);
mParams.add(wparams);
}
try {
root.setView(view, wparams, panelParentView);
} catch (RuntimeException e) {
// who care?
}
}给我们的View设置参数并添加到mRoots中，由WindowManagerGlobal进行管理，之后的事情就和View没什么关系了。接着调用ViewRootImpl#setView()。跟进。下面是个关键点，同学们注意力要集中。
源码位置：frameworks/base/core/Java/Android/view/ViewRootImpl.java
ViewRootImpl#setView()
public void setView(View view, WindowManager.LayoutParams attrs, View panelParentView) {
synchronized (this) {
// 各种属性读取，赋值及效验
...
try {
...
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(),
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mInputChannel);
} catch (RemoteException e) {
...
}
mWindowSession是IWindowSession对象。在创建ViewRootImpl对象时被实例化。
public ViewRootImpl(Context context, Display display) {
mWindowSession = WindowManagerGlobal.getWindowSession();
...
}跟进。
源码位置：frameworks/base/core/Java/Android/view/WindowManagerGlobal.java
WindowManagerGlobal#getWindowSession()
public static IWindowSession getWindowSession() {
synchronized (WindowManagerGlobal.class) {
if (sWindowSession == null) {
try {
InputMethodManager imm = InputMethodManager.getInstance();
IWindowManager windowManager = getWindowManagerService();
sWindowSession = windowManager.openSession(
new IWindowSessionCallback.Stub() {
@Override
public void onAnimatorScaleChanged(float scale) {
ValueAnimator.setDurationScale(scale);
}
},
imm.getClient(), imm.getInputContext());
} catch (RemoteException e) {
Log.e(TAG, "Failed to open window session", e);
}
}
return sWindowSession;
}
}这里getWindowManagerService()通过AIDL返回WindowManagerService实例。之后调用WindowManagerService#openSession()。跟进。
源码位置：frameworks/base/services/java/com/android/server/wm/WindowManagerService.java
WindowManagerService#getWindowSession()
public IWindowSession openSession(IWindowSessionCallback callback, IInputMethodClient client,
IInputContext inputContext) {
if (client == null) throw new IllegalArgumentException("null client");
if (inputContext == null) throw new IllegalArgumentException("null inputContext");
Session session = new Session(this, callback, client, inputContext);
return session;
}返回一个Session对象。也就是说在ViewRootImpl#setView()中调用的是Session#addToDisplay()。跟进。
源码位置：frameworks/base/services/java/com/android/server/wm/Session.java
Session#addToDisplay()
@Override
public int addToDisplay(IWindow window, int seq, WindowManager.LayoutParams attrs,
int viewVisibility, int displayId, Rect outContentInsets, Rect outStableInsets,
Rect outOutsets, InputChannel outInputChannel) {
return mService.addWindow(this, window, seq, attrs, viewVisibility, displayId,
outContentInsets, outStableInsets, outOutsets, outInputChannel);
}这里的mService是个WindowManagerService对象，也就是说最后调用的是WindowManagerService#addWindow()。
源码位置：frameworks/base/services/java/com/android/server/wm/WindowManagerService.java
WindowManagerService#addWindow()
public int addWindow(...) {
...
WindowState win = new WindowState(this, session, client, token,
attachedWindow, appOp[0], seq, attrs, viewVisibility, displayContent);
win.attach();
mWindowMap.put(client.asBinder(), win);
...
}mWindowMap是个Map实例，将WindowManager添加进WindowManagerService统一管理。至此，整个添加视图操作解析完毕。
WindowManager.updateViewLayout()解析
和addView()过程一样，最终会进入到WindowManagerGlobal#updateViewLayout()。
源码位置：frameworks/base/core/Java/Android/view/WindowManagerGlobal.java
WindowManagerGlobal#getWindowSession()
if (view == null) {
throw new IllegalArgumentException("view must not be null");
}
if (!(params instanceof WindowManager.LayoutParams)) {
throw new IllegalArgumentException("Params must be WindowManager.LayoutParams");
}
final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams)params;
view.setLayoutParams(wparams);
synchronized (mLock) {
int index = findViewLocked(view, true);
ViewRootImpl root = mRoots.get(index);
mParams.remove(index);
mParams.add(index, wparams);
root.setLayoutParams(wparams, false);
}将传入的View设置参数之后，更新mRoot中View的参数。没撒好说的。next one。
WindowManager.removeView()解析
和上两个过程一样，最终会进入到WindowManagerGlobal#removeView()。
public void removeView(View view, boolean immediate) {
if (view == null) {
throw new IllegalArgumentException("view must not be null");
}
synchronized (mLock) {
int index = findViewLocked(view, true);
View curView = mRoots.get(index).getView();
removeViewLocked(index, immediate);
if (curView == view) {
return;
}
throw new IllegalStateException("Calling with view " + view
+ " but the ViewAncestor is attached to " + curView);
}
}
private void removeViewLocked(int index, boolean immediate) {
ViewRootImpl root = mRoots.get(index);
View view = root.getView();
...
boolean deferred = root.die(immediate);
if (view != null) {
view.assignParent(null);
if (deferred) {
mDyingViews.add(view);
}
}
}这个过程要稍微麻烦点，首先调用root.die()，接着将View添加进mDyingViews。跟进。
源码位置：frameworks/base/core/java/android/view/ViewRootImpl.java
ViewRootImpl#die()
boolean die(boolean immediate) {
...
mHandler.sendEmptyMessage(MSG_DIE);
return true;
}这里的参数immediate默认为false,也就是说这里只是发送了一个what=MSG_DIE的空消息。ViewRootHandler收到这条消息会执行doDie()。
void doDie() {
checkThread();
...
WindowManagerGlobal.getInstance().doRemoveView(this);
}跟进。
void doRemoveView(ViewRootImpl root) {
synchronized (mLock) {
final int index = mRoots.indexOf(root);
if (index >= 0) {
mRoots.remove(index);
mParams.remove(index);
final View view = mViews.remove(index);
mDyingViews.remove(view);
}
}
if (HardwareRenderer.sTrimForeground && HardwareRenderer.isAvailable()) {
doTrimForeground();
}
}经过一圈效验最终还是回到WindowManagerGlobal中移除View。
至此，本文已经全部结束，感谢耐心阅读到最后～
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