Screenshot of View is always null. Android

Question

In an android app i am trying to take a screenshot of a View called Sierpinski Triangle. However, the bitmap always comes back null. Sierpinski Triangle only has graphics from the onDraw method(no buttons, textviews, background...) Here is my code:

        sierpinskiTriangle.setDrawingCacheEnabled(true);
        sierpinskiTriangle.buildDrawingCache(true);
        sierpinskiTriangle.setDrawingCacheQuality(2);
        sierpinskiTriangle.measure(MeasureSpec.makeMeasureSpec(50, MeasureSpec.UNSPECIFIED), 
        MeasureSpec.makeMeasureSpec(50, MeasureSpec.UNSPECIFIED));
        sierpinskiTriangle.layout(0, 0, sierpinskiTriangle.getMeasuredWidth(), sierpinskiTriangle.getMeasuredHeight());
        Bitmap screensaver =sierpinskiTriangle.getDrawingCache(true);
        Bitmap screenshot = Bitmap.createBitmap(this.sierpinskiTriangle.getWidth(), this.sierpinskiTriangle.getHeight(), Config.ARGB_8888);

Please help, I have been going at this for hours.

Here is the code of Sierpinski Triangle:

package com.Marco.Fractal;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Bitmap.Config;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.RectShape;
import android.view.View;

public class SierpinskiTriangle extends View{


Paint paint = new Paint();
int stage;
int width;
int height;
int h1, h2, w1, w2,w3;

public SierpinskiTriangle(Context context, int t, int s, int w, int h) {
super(context);
stage = s;
width=w;
height=h;
paint.setColor(Color.RED);
h1=(int)(height/2-((((width-30)/4)*1.732)));
h2=(int)(height/2+((((width-30)/4)*1.732)));
w1=15;
w2=width-15;
w3=width/2;
}

protected void onDraw(final Canvas canvas) {

    this.setDrawingCacheEnabled(true);
    this.buildDrawingCache(true);
    canvas.drawLine(w1, h2, w3, (float) h1, paint);
    canvas.drawLine(w2, h2, w3, (float) h1, paint);
    canvas.drawLine(w1, h2, w2, h2, paint);
    triangles(canvas, w1, h2, w3, h1, w2, h2, stage);



}
protected void triangles(final Canvas canvas, int x1, int y1, int x2, int y2, int x3, int y3, int r)
{
    if(r==0)
    {
        canvas.drawLine(x1, y1, x2, y2, paint);
        canvas.drawLine(x2, y2, x3, y3, paint);
        canvas.drawLine(x3, y3, x1, y1, paint);
    }
    else
    {
        int xm1 = (x1+x2)/2;
        int xm2 = (x2+x3)/2;
        int xm3 = (x1+x3)/2;
        int ym1 = (y1+y2)/2;
        int ym2 = (y2+y3)/2;
        int ym3 = (y1+y3)/2;
        triangles(canvas, x1, y1, xm1, ym1, xm3,ym3, r-1);
        triangles(canvas, xm3, ym3,xm2, ym2, x3, y3, r-1);
        triangles(canvas, xm1, ym1, x2,y2, xm2,ym2,r-1);
    }
}

}

score 0 · Answer 1 · edited May 23 '17 at 12:12

0

[EDIT2]

I have a feeling the following 2 lines in your onDraw method are messing you up:

this.setDrawingCacheEnabled(true);     
this.buildDrawingCache(true);

Try removing them and see what happens!!!

[EDIT1] Try simplifying your code from all of what you have to simply:

Bitmap screenshot;
sierpinskiTriangle.setDrawingCacheEnabled(true);
screenshot = Bitmap.createBitmap(sierpinskiTriangle.getDrawingCache(true));
sierpinskiTriangle.setDrawingCacheEnabled(false);

[ORIGINAL]

Try:

Bitmap screenshot = Bitmap.createBitmap(sierpinskiTriangle.getDrawingCache(true));

Also Look here:

How to programmatically take a screenshot in Android?

edited May 23 '17 at 12:12

Community

1
1

answered Jun 29 '12 at 13:41

trumpetlicks

7,033
2
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Thank you but the line didn't work, could I be missing a permission? – user1491280 Jun 29 '12 at 13:46
WOW, interesting problem! +1, What is the code for the view sierpinskiTriangle? – trumpetlicks Jun 29 '12 at 14:03
Its long so I have to add it in two comments: – user1491280 Jun 29 '12 at 14:08
I added the code for sierpinskiTriangle in the original question – user1491280 Jun 29 '12 at 14:16
Try some of the things shown on this site, NOW IM JUST INTERESTED :-) http://android-yfchung.blogspot.com/2011/06/translation-among-bitmap-drawable.html – trumpetlicks Jun 29 '12 at 21:10

score 0 · Answer 2 · answered Jun 30 '12 at 18:04

Thank you buys for all the help, I finally fixed the problem.

I added this code to sierpinski triangle:

   public Bitmap getBitmap()
    {
        Bitmap b = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        Canvas c = new Canvas(b);
        draw(c);
        return b;
    }

This takes the screenshot but it zooms in when it takes the screen shot. I'll post if I find a solution to this problem

Screenshot of View is always null. Android

2 Answers2