Android 实现Activity后台运行

 @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {    if (keyCode == KeyEvent.KEYCODE_BACK) {    PackageManager pm = getPackageManager();    ResolveInfo homeInfo = pm.resolveActivity(new Intent(Intent.ACTION_MAIN).addCategory(Intent.CATEGORY_HOME), 0);    ActivityInfo ai = homeInfo.activityInfo;Intent startIntent = new Intent(Intent.ACTION_MAIN);startIntent.addCategory(Intent.CATEGORY_LAUNCHER);startIntent.setComponent(new ComponentName(ai.packageName, ai.name));startActivitySafely(startIntent);    return true;    }    return super.onKeyDown(keyCode, event);    } private void startActivitySafely(Intent intent) {      intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);      try {      startActivity(intent);      } catch (ActivityNotFoundException e) {      Toast.makeText(this, "没正常启动", Toast.LENGTH_SHORT).show();      } catch (SecurityException e) {      Toast.makeText(this, "存在安全隐患",      Toast.LENGTH_SHORT).show();      Log.e(MYLOG,"Launcher does not have the permission to launch "      + intent      + ". Make sure to create a MAIN intent-filter for the corresponding activity "      + "or use the exported attribute for this activity.",      e);      }      }  

 

 

下面是在通知栏开启一个已经启动的Activity

public void createNotification() {//int icon = android.R.drawable.ic_menu_revert;int icon = R.drawable.icon;Notification notification = new Notification(icon, "", notificationId);notification.flags = Notification.FLAG_ONLY_ALERT_ONCE;notification.setLatestEventInfo(context, "", "", receiveIntent());RemoteViews contentView = new RemoteViews(context.getPackageName(), R.layout.app_notification_layout);notification.contentView = contentView;notfionMgr.notify(notificationId, notification);}private PendingIntent receiveIntent() {Intent appIntent = new Intent(Intent.ACTION_MAIN);appIntent.addCategory(Intent.CATEGORY_LAUNCHER);appIntent.setComponent(new ComponentName(context.getPackageName(),context.getPackageName() + "." + localClassName));appIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);appIntent.setFlags(Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);appIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);PendingIntent contentIntent = PendingIntent.getActivity(context, notificationId, appIntent, PendingIntent.FLAG_UPDATE_CURRENT);//Intent intent = new Intent(context, HomeActivity.class);////intent.putExtra(NONE_START_APP, NONE);//intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);//PendingIntent contentIntent = PendingIntent.getActivity(context, notificationId, intent, PendingIntent.FLAG_UPDATE_CURRENT);return contentIntent;}