How to switch to other running application

I want to 开发者_开发问答write a application to switch to other running application, like "Switch to" on "Windows Task Manager".

I already have it's package name, process name, pid, label. But I don't know how to switch to it. Pls help me! Thank U!

P/S: I'm thinking about use Intent, but Intent.setClassName (String pkname, String cls name) need class name and i don't know how to get it.

That is an easy one.

    ActivityManager am = (ActivityManager) inst.getSystemService(Context.ACTIVITY_SERVICE);
    for(RunningTaskInfo t: am.getRunningTasks(10)){
        String packageName = t.topActivity.getPackageName();
        String className = t.topActivity.getClassName();
    }
    //Which one do you want?
    //Could also just do
    String packageName = am.getRunningTasks(1).get(0).topActivity.getPackageName();
    String className = am.getRunningTasks(1).get(0).topActivity.getClassName();

    //then
    startActivity(new Intent().setClassName(packageName, className).addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

    //Keep in mind you will need to declare the following permission in your AndroidManifest.xml
    android.Manifest.permission.GET_TASKS 

Using

List<ActivityManager.RunningTaskInfo> getRunningTasks();

Returns a list of tasks that are running on the device.

If you look at the RunningTaskInfo API, there is a field public ComponentName baseActivity

ComponentName, on has these two public methods:

String getClassName()

Return the class name of this component.

String getPackageName()

Return the package name of this component.

     ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);
     for (ActivityManager.RunningTaskInfo info : am.getRunningTasks(9999)){
         int id = info.id;
         Log.d ("AM", "ID: " + id);
         String name = info.baseActivity.getClassName();
         Log.d ("AM", "Class: " + name);
     }