title: Android：why setText can work on the work Thread
body: <p>I found that <code>setText</code> can work on the work thread on high version SDK.<br>
  Why is this code not crashing on high version SDK?</p>
  
  <pre><code>final TextView mTestTv = findViewById(R.id.ratio);
  mTestTv.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
          new Thread(new Runnable() {
              @Override
              public void run() {
                  mTestTv.setText("test");
              }
          }).start();
  
      }
  });
  </code></pre>