Saving a chart as an image in MPAndroidChart

Question

I am using the MPAndroidChart to render various charts. I wanted to add the functionality of saving the charts as images to the gallery. I added an icon to the action bar to use this functionality, but the image does not save to the gallery.

The code is given below :

<item android:id="@+id/save"
    android:icon="@drawable/ic_action_accept"
    android:title="@string/save"
    app:showAsAction="always"/>

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

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    switch (item.getItemId()) {
        case R.id.save :
            mlineChart.saveToGallery("Chart",50);
            return true;
        case R.id.action_settings :
            return true;
        default: return super.onOptionsItemSelected(item);
    }
}

do you have write external storage permission in your manifest — King of Masses, Apr 24 '15 at 11:26

King of Masses · Accepted Answer · 2019-11-07T09:43:55.037

From How to programatically take a screenshot on Android?

// image naming and path  to include sd card  appending name you choose for file
String mPath = Environment.getExternalStorageDirectory().toString() + "/" + ACCUWX.IMAGE_APPEND;   
// create bitmap screen capture
Bitmap bitmap;
View v1 = mWebview.getRootView(); // take the view from your webview
v1.setDrawingCacheEnabled(true);
bitmap = Bitmap.createBitmap(v1.getDrawingCache());
v1.setDrawingCacheEnabled(false);

OutputStream fout = null;
imageFile = new File(mPath);

try {
  fout = new FileOutputStream(imageFile);
  bitmap.compress(Bitmap.CompressFormat.JPEG, 90, fout);
  fout.flush();
  fout.close();

} catch (FileNotFoundException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
} catch (IOException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
}

Update

Thanks tamim for pointing this deprecation out. Here is the updated solution

public void setDrawingCacheEnabled (boolean enabled)

This method was deprecated in API level 28. The view drawing cache was largely made obsolete with the introduction of hardware-accelerated rendering in API 11. With hardware-acceleration, intermediate cache layers are largely unnecessary and can easily result in a net loss in performance due to the cost of creating and updating the layer. In the rare cases where caching layers are useful, such as for alpha animations, setLayerType(int, android.graphics.Paint) handles this with hardware rendering. For software-rendered snapshots of a small part of the View hierarchy or individual Views it is recommended to create a Canvas from either a Bitmap or Picture and call draw(android.graphics.Canvas) on the View. However these software-rendered usages are discouraged and have compatibility issues with hardware-only rendering features such as Config.HARDWARE bitmaps, real-time shadows, and outline clipping. For screenshots of the UI for feedback reports or unit testing the PixelCopy API is recommended.

So as per the recommendations use PixelCopy for fetching screenshots / snapshot of the UI.It's available in API level 24 and above

PixelCopy.request(surfaceViewObject,BitmapDest,listener,new Handler());

where,

surfaceViewObject is the object of surface view

BitmapDest is the bitmap object where the image will be saved and it cant be null

listener is OnPixelCopyFinishedListener

for more info refer Pixel Copy Android Documentation

setdrawingcacheenabled is now deprecated on api 28, is there an other approach we can use safely? — Tamim Attafi, Nov 07 '19 at 09:09
Thanks for the solution. check my answer if you want to achieve this without the usage of PixelCopy, because in some cases you need the bitmap directly and not through a callback. — Tamim Attafi, Nov 07 '19 at 12:19

score 2 · Answer 2 · answered Nov 07 '19 at 12:17

Using Kotlin extentions, I was able to achieve it this way:

//create a bitmap using view height and width to draw to it
fun View.getBitmap(): Bitmap = Bitmap.createBitmap(measuredWidth, measuredHeight, Bitmap.Config.ARGB_8888).also {
    //create a canvas for this bitmap (it)
    Canvas(it).apply {
        //if the view has a background, draw it to the canvas, else draw a white screen 
        //because canvas default background is black
        background?.draw(this) ?: drawColor(Color.WHITE)
        //draw the view to the canvas
        draw(this)
    }
}

The reason I used measuredWidth and Height is because when you have a scrollable view or a ViewGroup the screenshot is clipped.

Saving a chart as an image in MPAndroidChart

2 Answers2