java - What is the rendering completion event of View?

Question

Problem Description

Now there is such a simple Fragment:

public class Level1Fragment extends Fragment {
    TextView tv;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        ViewGroup v=inflater.inflate(R.layout.activity_test,null);
        tv= (TextView) v.findViewById(R.id.level1_textview);
        tv.setText("啦啦啦");
        return v;
    }
    //给View截图，代码应该没有问题
    public static Bitmap convertViewToBitmap(View view){
        view.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED), View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
        view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
        view.buildDrawingCache();
        return view.getDrawingCache();
    }
    

Now, I want to get a screenshot of this TextView when the Fragment has just been loaded. In which event should I put the code?

Try to solve

I've tried tv.postDelayed(), tv.post() and tv.getViewTreeObserver().addOnPreDrawListener().

Please also post the code you tried:

@Override
    public void onResume() {
        super.onResume();
        tv.postDelayed(new Runnable() {
            @Override
            public void run() {
                final Bitmap bit=convertViewToBitmap(tv);
                //iv只是个简单的ImageView，与本问题无关
                iv.setImageBitmap(bit);
                iv.startAnimation(new AlphaAnimation(1,0));
            }
        },100);

    }

But they cannot be obtained.

question

So, what method should be used to correctly obtain the screenshot of tv?

(btw, Fragment is displayed directly through FragmentTransaction.replace(), not through ViewPager, so the life cycle should not be disrupted..)

Solve your doubts!

Answer 1

The first two of the three methods you mentioned are OK, but there is a problem with the last one, which should be getViewTreeObserver().addOnGlobalLayoutListener()