[android] How to capture the android device screen content?

Possible Duplicate:
How to programatically take a screenshot on Android?

How to capture the android device screen content and make an image file using the snapshot data? Which API should I use or where could I find related resources?

BTW: not camera snapshot, but device screen

You can try the following library: Android Screenshot Library (ASL) enables to programmatically capture screenshots from Android devices without requirement of having root access privileges. Instead, ASL utilizes a native service running in the background, started via the Android Debug Bridge (ADB) once per device boot.

Framebuffer seems the way to go, it will not always contain 2+ frames like mentioned by Ryan Conrad. In my case it contained only one. I guess it depends on the frame/display size.

I tried to read the framebuffer continuously but it seems to return for a fixed amount of bytes read. In my case that is (3 410 432) bytes, which is enough to store a display frame of 854*480 RGBA (3 279 360 bytes). Yes, the frame in binary outputed from fb0 is RGBA in my device. This will most likely depend from device to device. This will be important for you to decode it =)

In my device /dev/graphics/fb0 permissions are so that only root and users from group graphics can read the fb0. graphics is a restricted group so you will probably only access fb0 with a rooted phone using su command.

Android apps have the user id (uid) app_## and group id (guid) app_## .

adb shell has uid shell and guid shell, which has much more permissions than an app. You can actually check those permissions at /system/permissions/platform.xml

This means you will be able to read fb0 in the adb shell without root but you will not read it within the app without root.

Also, giving READ_FRAME_BUFFER and/or ACCESS_SURFACE_FLINGER permissions on AndroidManifest.xml will do nothing for a regular app because these will only work for 'signature' apps.

[Based on Android source code:]

At the C++ side, the SurfaceFlinger implements the captureScreen API. This is exposed over the binder IPC interface, returning each time a new ashmem area that contains the raw pixels from the screen. The actual screenshot is taken through OpenGL.

For the system C++ clients, the interface is exposed through the ScreenshotClient class, defined in <surfaceflinger_client/SurfaceComposerClient.h> for Android < 4.1; for Android > 4.1 use <gui/SurfaceComposerClient.h>

Before JB, to take a screenshot in a C++ program, this was enough:

ScreenshotClient ssc;
ssc.update();

With JB and multiple displays, it becomes slightly more complicated:

ssc.update(
    android::SurfaceComposerClient::getBuiltInDisplay(
        android::ISurfaceComposer::eDisplayIdMain));

Then you can access it:

do_something_with_raw_bits(ssc.getPixels(), ssc.getSize(), ...);

Using the Android source code, you can compile your own shared library to access that API, and then expose it through JNI to Java. To create a screen shot form your app, the app has to have the READ_FRAME_BUFFER permission. But even then, apparently you can create screen shots only from system applications, i.e. ones that are signed with the same key as the system. (This part I still don't quite understand, since I'm not familiar enough with the Android Permissions system.)

Here is a piece of code, for JB 4.1 / 4.2:

#include <utils/RefBase.h>
#include <binder/IBinder.h>
#include <binder/MemoryHeapBase.h>
#include <gui/ISurfaceComposer.h>
#include <gui/SurfaceComposerClient.h>

static void do_save(const char *filename, const void *buf, size_t size) {
    int out = open(filename, O_RDWR|O_CREAT, 0666);
    int len = write(out, buf, size);
    printf("Wrote %d bytes to out.\n", len);
    close(out);
}

int main(int ac, char **av) {
    android::ScreenshotClient ssc;
    const void *pixels;
    size_t size;
    int buffer_index;

    if(ssc.update(
        android::SurfaceComposerClient::getBuiltInDisplay(
            android::ISurfaceComposer::eDisplayIdMain)) != NO_ERROR ){
        printf("Captured: w=%d, h=%d, format=%d\n");
        ssc.getWidth(), ssc.getHeight(), ssc.getFormat());
        size = ssc.getSize();
        do_save(av[1], pixels, size);
    }
    else
        printf(" screen shot client Captured Failed");
    return 0;
}

AFAIK, All of the methods currently to capture a screenshot of android use the /dev/graphics/fb0 framebuffer. This includes ddms. It does require root to read from this stream. ddms uses adbd to request the information, so root is not required as adb has the permissions needed to request the data from /dev/graphics/fb0.

The framebuffer contains 2+ "frames" of RGB565 images. If you are able to read the data, you would have to know the screen resolution to know how many bytes are needed to get the image. each pixel is 2 bytes, so if the screen res was 480x800, you would have to read 768,000 bytes for the image, since a 480x800 RGB565 image has 384,000 pixels.

if you want to do screen capture from Java code in Android app AFAIK you must have Root provileges.

For newer Android platforms, one can execute a system utility screencap in /system/bin to get the screenshot without root permission. You can try /system/bin/screencap -h to see how to use it under adb or any shell.

By the way, I think this method is only good for single snapshot. If we want to capture multiple frames for screen play, it will be too slow. I don't know if there exists any other approach for a faster screen capture.

Use the following code:

Bitmap bitmap;
View v1 = MyView.getRootView();
v1.setDrawingCacheEnabled(true);
bitmap = Bitmap.createBitmap(v1.getDrawingCache());
v1.setDrawingCacheEnabled(false);

Here MyView is the View through which we need include in the screen. You can also get DrawingCache from of any View this way (without getRootView()).

There is also another way..
If we having ScrollView as root view then its better to use following code,

LayoutInflater inflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE);
FrameLayout root = (FrameLayout) inflater.inflate(R.layout.activity_main, null); // activity_main is UI(xml) file we used in our Activity class. FrameLayout is root view of my UI(xml) file.
root.setDrawingCacheEnabled(true);
Bitmap bitmap = getBitmapFromView(this.getWindow().findViewById(R.id.frameLayout)); // here give id of our root layout (here its my FrameLayout's id)
root.setDrawingCacheEnabled(false);

Here is the getBitmapFromView() method

public static Bitmap getBitmapFromView(View view) {
        //Define a bitmap with the same size as the view
        Bitmap returnedBitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(),Bitmap.Config.ARGB_8888);
        //Bind a canvas to it
        Canvas canvas = new Canvas(returnedBitmap);
        //Get the view's background
        Drawable bgDrawable =view.getBackground();
        if (bgDrawable!=null) 
            //has background drawable, then draw it on the canvas
            bgDrawable.draw(canvas);
        else 
            //does not have background drawable, then draw white background on the canvas
            canvas.drawColor(Color.WHITE);
        // draw the view on the canvas
        view.draw(canvas);
        //return the bitmap
        return returnedBitmap;
    }

It will display entire screen including content hidden in your ScrollView


UPDATED AS ON 20-04-2016

There is another better way to take screenshot.
Here I have taken screenshot of WebView.

WebView w = new WebView(this);
    w.setWebViewClient(new WebViewClient()
    {
        public void onPageFinished(final WebView webView, String url) {

            new Handler().postDelayed(new Runnable(){
                @Override
                public void run() {
                    webView.measure(View.MeasureSpec.makeMeasureSpec(
                                    View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED),
                            View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
                    webView.layout(0, 0, webView.getMeasuredWidth(),
                            webView.getMeasuredHeight());
                    webView.setDrawingCacheEnabled(true);
                    webView.buildDrawingCache();
                    Bitmap bitmap = Bitmap.createBitmap(webView.getMeasuredWidth(),
                            webView.getMeasuredHeight(), Bitmap.Config.ARGB_8888);

                    Canvas canvas = new Canvas(bitmap);
                    Paint paint = new Paint();
                    int height = bitmap.getHeight();
                    canvas.drawBitmap(bitmap, 0, height, paint);
                    webView.draw(canvas);

                    if (bitmap != null) {
                        try {
                            String filePath = Environment.getExternalStorageDirectory()
                                    .toString();
                            OutputStream out = null;
                            File file = new File(filePath, "/webviewScreenShot.png");
                            out = new FileOutputStream(file);

                            bitmap.compress(Bitmap.CompressFormat.PNG, 50, out);
                            out.flush();
                            out.close();
                            bitmap.recycle();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            }, 1000);
        }
    });

Hope this helps..!