Take screenshot

问题:

I am working on an app, which uses the frontcamera to simulate a mirror for the person using the app. I have implemented a "Head-up-Display" which is in front of the cameraview and displays some stuff. This works fine at the moment. Now I'd like to implement a method to take a screenshot every 5s.

But how to take a screenshot? I tried one possible solution, but this just takes a screenshot of the HuD without the mirror, because I have to pass a view (v1) to this method:

    // create bitmap screen capture
    Bitmap b1;

    View v1 = (RelativeLayout) findViewById(R.id.RelLayout);
    v1.setDrawingCacheEnabled(true);
    b1 = Bitmap.createBitmap(v1.getDrawingCache());
    v1.setDrawingCacheEnabled(false);

    //mPreviewLayout.setDrawingCacheEnabled(true);
    //mPreviewLayout.buildDrawingCache();
    //Bitmap b1 = mPreviewLayout.getDrawingCache();

    String path = Environment.getExternalStorageDirectory().toString();
    FileOutputStream out = null;
    try {
        File file = new File(path, "brushGuide" + instructionCounter + ".jpg");
        out = new FileOutputStream(file);
        b1.compress(Bitmap.CompressFormat.PNG, 90, out);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            out.close();
        } catch (Throwable ignore) {
        }
    }

My layout and the important code for this question is quite less:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 
    android:id="@+id/RelLayout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_horizontal" >

<FrameLayout
    android:id="@+id/camPreview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true" >
</FrameLayout>

 <ImageView android:id="@+id/imageView"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginTop="80dp"
          android:layout_marginLeft="65dp"
          ></ImageView>

</RelativeLayout>

onCreate()

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

 // do we have a camera?
 if (!getPackageManager()
        .hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
    Toast.makeText(this,
            "No camera feature on this device. App closing",
            Toast.LENGTH_LONG).show();
 }else{

    mCameraId = findFirstFrontFacingCamera();

    if (mCameraId >= 0) {
        // Kamera wurde gefunden
        mPreviewLayout = (FrameLayout) findViewById(R.id.camPreview);
        mPreviewLayout.removeAllViews();
        startCameraInLayout(mPreviewLayout, mCameraId);
    }
  }
}

Is even possible to just take a normal screenshot of the actual content of the devices display without rooting the device, and if yes: How?

Any help will be appreciated.

回答1:

I actually just did this the other day and it was a pain to get a screenshot of the entire Activity, while also making sure to remove the StatusBar from the image (as it will appear as a black rectangle in the drawing cache). This method will also allow you to overlay the returned image with some color (ie. fading)):

public static Bitmap getActivitySnapshot(Activity activity, boolean fade){
    View view = activity.getWindow().getDecorView();
    view.setDrawingCacheEnabled(true);
    Bitmap bmap = view.getDrawingCache();

    Rect statusBar = new Rect();
    activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(statusBar);
    Bitmap snapshot = Bitmap.createBitmap(bmap, 0, statusBar.top, bmap.getWidth(), bmap.getHeight() - statusBar.top, null, true);

    if(fade && snapshot != null){
        Canvas canvas = new Canvas(snapshot);
        Paint paint = new Paint();
        paint.setColor(Color.parseColor("#88121212"));
        canvas.drawRect(0, 0, snapshot.getWidth(), snapshot.getHeight(), paint);
    }

    view.setDrawingCacheEnabled(false);
    return snapshot;
}

If you don't want the fading part, the important parts would just be:

public static Bitmap getActivitySnapshot(Activity activity){
    View view = activity.getWindow().getDecorView();
    view.setDrawingCacheEnabled(true);
    Bitmap bmap = view.getDrawingCache();

    Rect statusBar = new Rect();
    activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(statusBar);
    Bitmap snapshot = Bitmap.createBitmap(bmap, 0, statusBar.top, bmap.getWidth(), bmap.getHeight() - statusBar.top, null, true);

    view.setDrawingCacheEnabled(false);
    return snapshot;
}

You may also want to catch the OutOfMemoryError that may be thrown when working with large Bitmaps.

回答2:

This code can help you.

    /**
 * @param v view to capture it may be any Layout
 * @return
 */
 public static Bitmap captureScreen(View v)
 {
 Bitmap bitmap = null;

 try {
 if(v!=null)
 {
 int width = v.getWidth();
 int height = v.getHeight();

 Bitmap screenshot = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
 v.draw(new Canvas(screenshot));
 }
 } catch (Exception e)
 {
 Log.d("captureScreen", "Failed");
 }

 return bitmap;
 }

回答3:

By screenshot, would a copy of your Root view help?

If so, you can use this:

public static Bitmap loadBitmapFromView(View view) {
    Bitmap bitmap = Bitmap.createBitmap(view.getLayoutParams().width, view.getLayoutParams().height, Bitmap.Config.ARGB_8888);                
    Canvas canvas = new Canvas(bitmap);
    view.layout(view.getLeft(), view.getTop(), view.getRight(), view.getBottom());
    view.draw(canvas);
    return bitmap;
}

Just pass your root view into this function and you can save the bitmap.