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                        /How-old 刷脸神器

把TextView转换成Bitmap报空指针异常

TextView tv = (TextView) mWaitting.findViewById(R.id.id_age_and_gender);
tv.setText(age+"");
Log.d("TAG","here");
if(isMale){
    tv.setCompoundDrawablesWithIntrinsicBounds(getResources().getDrawable(R.drawable.male),null,null,null);
}else {
    tv.setCompoundDrawablesWithIntrinsicBounds(getResources().getDrawable(R.drawable.female),null,null,null);
}
tv.setDrawingCacheEnabled(true);
Bitmap bitmap = Bitmap.createBitmap(tv.getDrawingCache());
tv.destroyDrawingCache();
return bitmap;

Bitmap bitmap = Bitmap.createBitmap(tv.getDrawingCache());这个位置报空指针异常，怎么办