在搜索了很多没有问题后，我需要你的帮助。我有一个演示应用程序可以使用连接到我的设备的第二个屏幕。我有应用程序的源代码，它们使用 Mediarouter 类和从 Presentation 类扩展的名为 LauncherSecondScreen 的类
我试图将应用程序作为一项服务来保持应用程序在后台运行，但 mediarouter 回调似乎只在主线程上运行（我不确定我只是 android dev 的初学者）。我有应用程序的完整代码：有两个布局活动，一个显示在主屏幕上，另一个显示在第二个屏幕上：
public class MainActivity extends Activity {
private final String TAG = "PresentationWithMediaRouterActivity";
private MediaRouter mMediaRouter;
private LauncherSecondScreen mPresentation;
private boolean mPaused;
/**
* Initialization of the Activity after it is first created. Must at least
* call {@link android.app.Activity#setContentView setContentView()} to
* describe what is to be displayed in the screen.
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
// Be sure to call the super class.
super.onCreate(savedInstanceState);
// Get the media router service.
mMediaRouter = (MediaRouter)getSystemService(Context.MEDIA_ROUTER_SERVICE);
// See assets/res/any/layout/presentation_with_media_router_activity.xml for this
// view layout definition, which is being set here as
// the content of our screen.
setContentView(R.layout.activity_main);
}
@Override
protected void onResume() {
// Be sure to call the super class.
super.onResume();
// Listen for changes to media routes.
mMediaRouter.addCallback(MediaRouter.ROUTE_TYPE_LIVE_VIDEO, mMediaRouterCallback);
// Update the presentation based on the currently selected route.
mPaused = false;
updatePresentation();
}
private void updatePresentation() {
// Get the current route and its presentation display.
MediaRouter.RouteInfo route = mMediaRouter.getSelectedRoute(
MediaRouter.ROUTE_TYPE_LIVE_VIDEO);
Display presentationDisplay = route != null ? route.getPresentationDisplay() : null;
// Dismiss the current presentation if the display has changed.
if (mPresentation != null && mPresentation.getDisplay() != presentationDisplay) {
Log.i(TAG, "Dismissing presentation because the current route no longer "
+ "has a presentation display.");
mPresentation.dismiss();
mPresentation = null;
}
// Show a new presentation if needed.
if (mPresentation == null && presentationDisplay != null) {
Log.i(TAG, "Showing presentation on display: " + presentationDisplay);
mPresentation = new LauncherSecondScreen(this, presentationDisplay);
mPresentation.setOnDismissListener(mOnDismissListener);
try {
mPresentation.show();
} catch (WindowManager.InvalidDisplayException ex) {
Log.w(TAG, "Couldn't show presentation! Display was removed in "
+ "the meantime.", ex);
mPresentation = null;
}
}
// Update the contents playing in this activity.
updateContents();
}
private void updateContents() {
// Show either the content in the main activity or the content in the presentation
// along with some descriptive text about what is happening.
if (mPresentation != null) {
if (mPaused) {
mPresentation.dismiss();//getSurfaceView().onPause();
} else {
mPresentation.show();//getSurfaceView().onResume();
}
} else {
/* mInfoTextView.setText("presentation_with_media_router_now_playing_locally");
mSurfaceView.setVisibility(View.VISIBLE);
if (mPaused) {
mSurfaceView.onPause();
} else {
mSurfaceView.onResume();
}*/
}
}
private final MediaRouter.SimpleCallback mMediaRouterCallback =
new MediaRouter.SimpleCallback() {
@Override
public void onRouteSelected(MediaRouter router, int type, RouteInfo info) {
Log.d(TAG, "onRouteSelected: type=" + type + ", info=" + info);
updatePresentation();
}
@Override
public void onRouteUnselected(MediaRouter router, int type, RouteInfo info) {
Log.d(TAG, "onRouteUnselected: type=" + type + ", info=" + info);
updatePresentation();
}
@Override
public void onRoutePresentationDisplayChanged(MediaRouter router, RouteInfo info) {
Log.d(TAG, "onRoutePresentationDisplayChanged: info=" + info);
updatePresentation();
}
};
/**
* Listens for when presentations are dismissed.
*/
private final DialogInterface.OnDismissListener mOnDismissListener =
new DialogInterface.OnDismissListener() {
@Override
public void onDismiss(DialogInterface dialog) {
if (dialog == mPresentation) {
Log.i(TAG, "Presentation was dismissed.");
mPresentation = null;
updateContents();
}
}
};
@SuppressLint({"NewApi"})
public class LauncherSecondScreen extends Presentation
{
public LauncherSecondScreen(Context paramContext, Display paramDisplay)
{
super(paramContext, paramDisplay/*,android.R.style.Theme_Holo_Light_Dialog_NoActionBar*/);
}
protected void onCreate(Bundle paramBundle)
{
super.onCreate(paramBundle);
setContentView(R.layout.dialog_second_screen_content);
//// this.iv_secondScreen_banner = ((ImageView)findViewById(R.id.titleImage));
}
}
}
该应用程序很好，它在主屏幕中显示一个视图，在第二个屏幕中显示第二个视图，但是当我将应用程序恢复为背景时，第二个屏幕会采用与第一个屏幕相同的视图。即使我恢复应用程序以使用另一个应用程序，我也想保持第二个视图显示在第二个屏幕中