手机截屏并用Dialog展示

public class MainActivity extends AppCompatActivity {
    ImageView image;
    Button button;
    Bitmap bitmap;
    Dialog dia;
    Context context;
    ImageView imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        context=this;
        image = (ImageView) findViewById(R.id.image);
        button = (Button) findViewById(R.id.button);


        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //截屏
                View view = getWindow().getDecorView();
                view.setDrawingCacheEnabled(true);
                view.buildDrawingCache();
                bitmap = view.getDrawingCache();
                //截屏后用Dialog展示
                showDialog(bitmap);



            }
        });
    }

    public void showDialog(Bitmap bitmap){
        dia = new Dialog(context, R.style.edit_AlertDialog_style);
        dia.setContentView(R.layout.activity_start_dialog);
        imageView=(ImageView) dia.findViewById(R.id.im);
        imageView.setImageBitmap(bitmap);
        dia.show();
    }
}