android:resizeableActivity="true"
android:supportsPictureInPicture="true"
android:configChanges="screenSize|smallestScreenSize|screenLayout|orientation"

PictureInPictureParams params = new PictureInPictureParams.Builder()
   .setAspectRatio(new Rational(10, 16))
   .build();

@Override
public void onPictureInPictureModeChanged(boolean isInPictureInPictureMode, Configuration newConfig) {
  super.onPictureInPictureModeChanged(isInPictureInPictureMode, newConfig);
  FrameLayout container = findViewById(R.id.local_video_view_container);
  SurfaceView surfaceView = (SurfaceView) container.getChildAt(0);
  surfaceView.setZOrderMediaOverlay(!isInPictureInPictureMode);
  surfaceView.setVisibility(isInPictureInPictureMode ? View.GONE : View.VISIBLE);
  container.setVisibility(isInPictureInPictureMode ? View.GONE : View.VISIBLE);
}

package com.example.myapplication;

import android.annotation.TargetApi;
import android.app.PictureInPictureParams;
import android.content.res.Configuration;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.util.Rational;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.TextView;

/**
 * 画中画
 */

public class TestPIPActivity extends AppCompatActivity {
  private static final String TAG = "TestPIPActivity";
  private PictureInPictureParams.Builder mPictureInPictureParamsBuilder;

  @TargetApi(Build.VERSION_CODES.O)
  @Override
  protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    FrameLayout content = new FrameLayout(this);
    setContentView(content,new ViewGroup.LayoutParams(
        ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));

    if(Build.VERSION.SDK_INT == Build.VERSION_CODES.O){
      mPictureInPictureParamsBuilder = new PictureInPictureParams.Builder();

      final TextView textView = new TextView(this);
      textView.setText("test PIP");
      textView.setTextSize(20);
      FrameLayout.LayoutParams fl = new FrameLayout.LayoutParams(
          ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
      fl.gravity = Gravity.CENTER ;
      textView.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {//主要操作
          Rational aspectRatio = new Rational(10,10);
          mPictureInPictureParamsBuilder.setAspectRatio(aspectRatio).build();
          enterPictureInPictureMode(mPictureInPictureParamsBuilder.build());
        }
      });
      content.addView(textView,fl);

    }else{
      TextView descTv = new TextView(this);
      descTv.setText("当前版本不支持...");
      descTv.setTextSize(20);
      FrameLayout.LayoutParams Tvfl = new FrameLayout.LayoutParams(
          ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
      Tvfl.gravity = Gravity.CENTER ;
      content.addView(descTv,Tvfl);
    }

  }



  @Override
  public void onPictureInPictureModeChanged(boolean isInPictureInPictureMode, Configuration newConfig) {
    super.onPictureInPictureModeChanged(isInPictureInPictureMode, newConfig);
    Log.d(TAG,String.valueOf(isInPictureInPictureMode));
  }