writing app to take a screenshot, and then save it to the gallery of my Android phone, but the saved screenshot is completely black

Question

Here is my Screenshot class. The app is saving the screenshot in my gallery, which is what I want, but the image is completely black! If you had any suggestions to make this work, they would be much appreciated! Thanks!

public class Screenshot extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

          // set event listener for the Save Contact Button
          Button button = 
             (Button) findViewById(R.id.button);
          button.setOnClickListener(buttonClicked);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.screenshot, menu);
        return true;
    }

       // responds to event generated when user clicks the Done Button
       OnClickListener buttonClicked = new OnClickListener() 
       {
          @Override
          public void onClick(View v) 
          {
              Bitmap bitmap = takeScreenshot();
              saveBitmap(bitmap);
           }         
       };


     public void saveBitmap(Bitmap bitmap) {
         LinearLayout mainLayout = (LinearLayout) findViewById(R.id.LinearLayout01);
         Bitmap b = Bitmap.createBitmap(mainLayout.getWidth(), mainLayout.getHeight(), 
                 Bitmap.Config.ARGB_8888);
         MediaStore.Images.Media.insertImage(getContentResolver(), b, "image.png" , "screenshot");
    }

    public Bitmap takeScreenshot() {
         View rootView = findViewById(android.R.id.content).getRootView();
         rootView.setDrawingCacheEnabled(true);
        return rootView.getDrawingCache();
        }
}

and here is my main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="@+id/LinearLayout01"
>
<Button
android:id="@+id/button"
android:layout_height = "wrap_content"
android:layout_width ="wrap_content"
android:text = "take screenshot"
android:onClick = "DoIt"
/>

<ImageView
android:id="@+id/eiffelTowerImageView"
android:layout_width="200dip"
android:layout_height="200dip"
android:layout_toRightOf="@+id/colosseumImageView"
android:src="@drawable/eiffeltower" />
</LinearLayout>

Answer 1

This Code Works like a Charm for me

private static Bitmap takeScreenShot(Activity activity) {
    View view = activity.getWindow().getDecorView();
    view.setDrawingCacheEnabled(true);
    view.buildDrawingCache();
    Bitmap b1 = view.getDrawingCache();
    Rect frame = new Rect();
    activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(frame);
    int statusBarHeight = frame.top;
    int width = activity.getWindowManager().getDefaultDisplay().getWidth();
    int height = activity.getWindowManager().getDefaultDisplay()
            .getHeight();

    Bitmap b = Bitmap.createBitmap(b1, 0, statusBarHeight, width, height
            - statusBarHeight);
    view.destroyDrawingCache();
    Log.e("Screenshot", "taken successfully");
    return b;

}

public void saveBitmap(Bitmap bitmap) {
    File imagePath = new File(Environment.getExternalStorageDirectory()
            + "/screenshot.png");
    FileOutputStream fos;
    try {
        fos = new FileOutputStream(imagePath);
        bitmap.compress(CompressFormat.JPEG, 100, fos);
        Log.e("Screenshot", "saved successfully");

        fos.flush();
        fos.close();
    } catch (FileNotFoundException e) {
        Log.e("GREC", e.getMessage(), e);
    } catch (IOException e) {
        Log.e("GREC", e.getMessage(), e);
    }

}

Get Activity in OnCreate()

Activity activity = (MainActivity) this;

Then Call these Function where ever you want

Bitmap bitmap = takeScreenShot(activity);
saveBitmap(bitmap);

Answer 2

Try this code :

public class MainActivity extends Activity {

    Button btn_shoot;
    int i = 0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);



        btn_shoot = (Button)findViewById(R.id.btn_shoot);
        btn_shoot.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {

                    View view = findViewById(R.id.relativelayout);
                    view = view.getRootView();
                    view.setDrawingCacheEnabled(true);

                      view.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED), 
                                MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));

                          view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight()); 

                    Bitmap bitmap = view.getDrawingCache();

                    BitmapDrawable bitmapDrawable = new BitmapDrawable(bitmap);
                    ImageView iv = (ImageView) findViewById(R.id.imageView1);
                    iv.setBackgroundDrawable(bitmapDrawable);

                    if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
                        //we check if external storage is available, otherwise display an error message to the user

                           File sdCard = Environment.getExternalStorageDirectory();
                           File directory = new File (sdCard.getAbsolutePath() + "/Tutorial_ScreenShot");
                           directory.mkdirs();

                           String filename = "screenshot" + i + ".jpg"; 
                           File yourFile = new File(directory, filename);

                           while (yourFile.exists()) {
                            i++;   
                            filename = "screenshot" + i + ".jpg"; 
                            yourFile = new File(directory, filename);
                           } 

                           if (!yourFile.exists()) {
                               if (directory.canWrite())
                               {
                                   try {
                                     FileOutputStream out = new FileOutputStream(yourFile, true);
                                     bitmap.compress(Bitmap.CompressFormat.PNG, 90, out);
                                     out.flush();
                                     out.close();
                                     Toast.makeText(MainActivity.this, "File exported to /sdcard/Tutorial_ScreenShot/screenshot" + i + ".jpg", Toast.LENGTH_SHORT).show();
                                     i++;
                                    } catch (IOException e) {
                                   e.printStackTrace();
                                }

                               }
                           }

                        }
                        else
                        {
                           Toast.makeText(MainActivity.this, "SD Card not available!", Toast.LENGTH_SHORT).show();
                        }


            }
        });

    }

}

Answer 3

Your solution will only work for taking a screenshot of your own app (since it uses the app's drawing cache), so if that's what you want to do, you'll have to make sure it's visible on the screen. Anything that your app doesn't have permission to view (like another app running behind it) will not show up or, as you're seeing, will show up black.

I suggest you look at this other screenshot question here to see the constraints under which you're working. Primarily, since you presumably don't have root permissions or a signature application (which would only be true if you compiled your own ROM), then you can't capture the framebuffer, which is what the native Android screenshot mechanism in 4.0+ can do for you if you press a specific key combination (on my Galaxy Nexus it's power+volume down).