Screenshot einer Activity erstellen und abspeichern

    //Begin own Code
    private int mBigThumbnailWidth = -1;
    private int mBigThumbnailHeight = -1;

    private final Bitmap createBigThumbnailBitmap(ActivityClientRecord r) {
        Bitmap bigThumbnail = null;
        try {
            int w = mBigThumbnailWidth;
            int h;
            if (w < 0) {
                Resources res = r.activity.getResources();
                mBigThumbnailHeight = h =
                    res.getDimensionPixelSize(com.android.internal.R.dimen.big_thumbnail_height);

                mBigThumbnailWidth = w =
                    res.getDimensionPixelSize(com.android.internal.R.dimen.big_thumbnail_width);
            } else {
                h = mBigThumbnailHeight;
            }

            // On platforms where we don't want thumbnails, set dims to (0,0)
            if ((w > 0) && (h > 0)) {
                View topView = r.activity.getWindow().getDecorView();

                // Maximize bitmap by capturing in native aspect.
                if (topView.getWidth() >= topView.getHeight()) {
                    bigThumbnail = Bitmap.createBitmap(w, h, THUMBNAIL_FORMAT);
                } else {
                    bigThumbnail = Bitmap.createBitmap(h, w, THUMBNAIL_FORMAT);
                }

                bigThumbnail.eraseColor(0);
                Canvas cv = new Canvas(bigThumbnail);
                if (!r.activity.onCreateThumbnail(bigThumbnail, cv)) {
                    bigThumbnail = null;
                }
            }

        } catch (Exception e) {
            if (!mInstrumentation.onException(r.activity, e)) {
                throw new RuntimeException(
                        "Unable to create bigThumbnail of "
                        + r.intent.getComponent().toShortString()
                        + ": " + e.toString(), e);
            }
            bigThumbnail = null;
        }

        return bigThumbnail;
    }
    //End own Code

private final void performStopActivityInner(ActivityClientRecord r,
            StopInfo info, boolean keepShown) {
        if (localLOGV) Slog.v(TAG, "Performing stop of " + r);
        if (r != null) {
            if (!keepShown && r.stopped) {
                if (r.activity.mFinished) {
                    // If we are finishing, we won't call onResume() in certain
                    // cases.  So here we likewise don't want to call onStop()
                    // if the activity isn't resumed.
                    return;
                }
                RuntimeException e = new RuntimeException(
                        "Performing stop of activity that is not resumed: "
                        + r.intent.getComponent().toShortString());
                Slog.e(TAG, e.getMessage(), e);
            }

            if (info != null) {
                try {
                    // First create a thumbnail for the activity...
                    info.thumbnail = createThumbnailBitmap(r);
                    info.description = r.activity.onCreateDescription();
                } catch (Exception e) {
                    if (!mInstrumentation.onException(r.activity, e)) {
                        throw new RuntimeException(
                                "Unable to save state of activity "
                                + r.intent.getComponent().toShortString()
                                + ": " + e.toString(), e);
                    }
                }
            }
            
            //Start of own Code
            
            Bitmap bigThumbnail = createBigThumbnailBitmap(r);
        	if (bigThumbnail != null){
        		try {
        			   FileOutputStream fos= r.activity.openFileOutput("applicationThumbnail.png",
        			      Context.MODE_WORLD_READABLE);

        			   bigThumbnail.compress(Bitmap.CompressFormat.PNG, 90, fos);

        			   fos.flush();
        			   fos.close();
        			   } catch (Exception e) {
        			   Log.e("BigThumbnailAddon", e.toString());
        			}
        	}
            //End of own Code

            if (!keepShown) {
                try {
                    // Now we are idle.
                    r.activity.performStop();
                } catch (Exception e) {
                    if (!mInstrumentation.onException(r.activity, e)) {
                        throw new RuntimeException(
                                "Unable to stop activity "
                                + r.intent.getComponent().toShortString()
                                + ": " + e.toString(), e);
                    }
                }
                r.stopped = true;
            }

            r.paused = true;
        }
    }

    <!-- The width that is used when creating big thumbnails of applications. -->
    <dimen name="big_thumbnail_width">381dp</dimen>
    <!-- The height that is used when creating big thumbnails of applications. -->
    <dimen name="big_thumbnail_height">240dp</dimen>

package com.felixl.TaskSwitcher;

import android.app.Activity;
import android.os.Bundle;
import android.app.ActivityManager;
import android.content.ActivityNotFoundException;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import static android.util.Log.d;
import java.util.List;

//import android.util.Log;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.ImageView;
import android.widget.LinearLayout;

public class TaskSwitcherMainActivity extends Activity implements OnClickListener {
	private static String LOG_TAG = "ATaskSwitcherMainActivity";
	private ActivityManager am;
	private PackageManager pm;
	private static String myfilename = "applicationThumbnail.png";
	private LinearLayout ll;
	private ImageView[] myImageViews;
	
	private static int NUM_BUTTONS = 8;
    private static int MAX_RECENT_TASKS = NUM_BUTTONS * 2; // lieber etwas zu viele, mache fallen weg.
    //WindowManager.FLAGDIMBEHIND benutzen? Leistung!
    
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        pm = this.getPackageManager();
        am = (ActivityManager) this.getSystemService( ACTIVITY_SERVICE );
        ll = (LinearLayout) findViewById(R.id.ll);
    }
    
    @Override
    public void onResume(){
    	super.onResume();
    	
    	myImageViews = new ImageView[NUM_BUTTONS];
    	ll.removeAllViews();
    	
    	Intent homeIntent = new Intent(Intent.ACTION_MAIN);
    	homeIntent.addCategory(Intent.CATEGORY_HOME);
    	ActivityInfo homeInfo = homeIntent.resolveActivityInfo(pm, 0);

        List<ActivityManager.RecentTaskInfo> recentTasks = am.getRecentTasks(MAX_RECENT_TASKS,2);//);2 = .RECENT_IGNORE_UNAVAILABLE, hidden FLAG);
        int index = 0;
        int numTasks = recentTasks.size();
        for (int i = 0; i < numTasks && (index < NUM_BUTTONS); ++i) {
            final ActivityManager.RecentTaskInfo info = recentTasks.get(i);

            Intent intent = new Intent(info.baseIntent);
            if (info.origActivity != null) {
                intent.setComponent(info.origActivity);
            }

            // Skip the current home activity.
            if (homeInfo != null) {
                if (homeInfo.packageName.equals(
                        intent.getComponent().getPackageName())
                        && homeInfo.name.equals(
                                intent.getComponent().getClassName())) {
                    continue;
                }
            }

            intent.setFlags((intent.getFlags()&~Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED)
                    | Intent.FLAG_ACTIVITY_NEW_TASK);
            final ResolveInfo resolveInfo = pm.resolveActivity(intent, 0);
            if (resolveInfo != null) {
                final ActivityInfo activityInfo = resolveInfo.activityInfo;
                final String title = activityInfo.loadLabel(pm).toString();
                
                final String myPackageName = activityInfo.packageName;

                if (title != null && title.length() > 0 && myPackageName != null) {
                	
                	String filelocation = "data/data/"+myPackageName+"/files";
                	
                	java.io.File file = new java.io.File(filelocation , myfilename);
                	Bitmap b = null;
                	if (file.exists()) {
                		d(LOG_TAG, "file exists");
                		b = BitmapFactory.decodeFile(filelocation+"/"+ myfilename);
                	}else{
                		d(LOG_TAG, "file doesn't exist: " + filelocation);
                		continue;
                	}
                	if (b != null){
                		d(LOG_TAG, "	Bitmap found: "+b);
        	        	ImageView iv = new ImageView(this);
        	        	ViewGroup.MarginLayoutParams mlp = new ViewGroup.MarginLayoutParams(b.getWidth(), b.getHeight());
        	        	mlp.setMargins(10, 10, 10, 10);
        	        	iv.setLayoutParams(mlp);
        	        	iv.setImageBitmap(b);
        	        	ll.addView(iv);
        	        	iv.setTag(intent);
        	        	iv.setOnClickListener(this);
        	        	myImageViews[index]=iv;
        	        	++index;
                	}
                }
            }
        }
    }
    
    @Override
    public boolean onCreateThumbnail(Bitmap bitmap,Canvas canvas){
    	return false; //Verhindert das diese App ein Thumbnail erstellt bekommt.
    }

	@Override
	 public void onClick(View v) {

		for (ImageView b: myImageViews){
            if (b != null && b == v) {
                // prepare a launch intent and send it
                Intent intent = (Intent)b.getTag();
                if (intent != null) {
                    intent.addFlags(Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY);
                    try {
                        this.startActivity(intent);
                    } catch (ActivityNotFoundException e) {
                        Log.w("Recent", "Unable to launch recent task", e);
                    }
                }
                break;
            }
        }
        finish();
    }
}

 . build/envsetup.sh && brunch blade