<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
 <VideoView
  android:id="@+id/video_view"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:clickable="false"
  android:focusable="false"
  android:focusableInTouchMode="false"/>
</LinearLayout>

 public class VideoViewActivity extends AppCompatActivity {
 private VideoView mVideoView;
 @Override
 protected void onCreate(@Nullable Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_video_view);
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
   getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
//   getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION);
  }
  mVideoView = (VideoView) findViewById(R.id.video_view);
  mVideoView.setVideoURI(Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.kr36));
  mVideoView.start();
  mVideoView.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
   @Override
   public void onCompletion(MediaPlayer mp) {
    mVideoView.start();
   }
  });
 }
}

...
<com.example.test.test_fitstatusbar.CustomVideoView
  android:id="@+id/custom_video_view"
...

public class CustomVideoView extends VideoView {
 public CustomVideoView(Context context) {
  super(context);
 }
 public CustomVideoView(Context context, AttributeSet attrs) {
  super(context, attrs);
 }
 public CustomVideoView(Context context, AttributeSet attrs, int defStyleAttr) {
  super(context, attrs, defStyleAttr);
 }
 @Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  int width = getDefaultSize(0, widthMeasureSpec);
  int height = getDefaultSize(0, heightMeasureSpec);
  setMeasuredDimension(width, height);
 }
}

/**
  * 1、UNSPECIFIED
  * 根据源码的注释,其大概意思是parent不对child做出限制.它想要什么size就给什么size.看了一些教程,都说用得很少,或者是系统内部才用得上.所以先不管了
  * 2、EXACTLY
  * 对应于match_parent和给出具体的数值
  * 3、AT_MOST
  * 对应于wrap_content
  */
 public static class MeasureSpec {
  private static final int MODE_SHIFT = 30;
  private static final int MODE_MASK = 0x3 << MODE_SHIFT;
  public static final int UNSPECIFIED = 0 << MODE_SHIFT;
  public static final int EXACTLY  = 1 << MODE_SHIFT;
  public static final int AT_MOST  = 2 << MODE_SHIFT;
　　　　 ......
  public static int getMode(int measureSpec) {
   return (measureSpec & MODE_MASK);
  }
  public static int getSize(int measureSpec) {
   return (measureSpec & ~MODE_MASK);
  }
　　　　 ......
 }

public static int getDefaultSize(int size, int measureSpec) {
  int result = size;
  int specMode = MeasureSpec.getMode(measureSpec);
  int specSize = MeasureSpec.getSize(measureSpec);
  switch (specMode) {
  case MeasureSpec.UNSPECIFIED:
   result = size;
   break;
  case MeasureSpec.AT_MOST:
  case MeasureSpec.EXACTLY:
   result = specSize;
   break;
  }
  return result;
 }

protected final void setMeasuredDimension(int measuredWidth, int measuredHeight) {
  boolean optical = isLayoutModeOptical(this);
  if (optical != isLayoutModeOptical(mParent)) {
   Insets insets = getOpticalInsets();
   int opticalWidth = insets.left + insets.right;
   int opticalHeight = insets.top + insets.bottom;
   measuredWidth += optical ? opticalWidth : -opticalWidth;
   measuredHeight += optical ? opticalHeight : -opticalHeight;
  }
  setMeasuredDimensionRaw(measuredWidth, measuredHeight);
 }

private void setMeasuredDimensionRaw(int measuredWidth, int measuredHeight) {
  mMeasuredWidth = measuredWidth;
  mMeasuredHeight = measuredHeight;
  mPrivateFlags |= PFLAG_MEASURED_DIMENSION_SET;
 }

@Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
//  Log.i("@@@@", "onMeasure(" + MeasureSpec.toString(widthMeasureSpec) + ", "
//    + MeasureSpec.toString(heightMeasureSpec) + ")");
  int width = getDefaultSize(mVideoWidth, widthMeasureSpec);
  int height = getDefaultSize(mVideoHeight, heightMeasureSpec);
　　　　 if (mVideoWidth > 0 && mVideoHeight > 0) {
   int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
   int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);
   int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
   int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);
　　　　　　　if (widthSpecMode == MeasureSpec.EXACTLY && heightSpecMode == MeasureSpec.EXACTLY) {
    // the size is fixed
    width = widthSpecSize;
    height = heightSpecSize;
    // for compatibility, we adjust size based on aspect ratio
    if ( mVideoWidth * height < width * mVideoHeight ) {
     //Log.i("@@@", "image too wide, correcting");
     width = height * mVideoWidth / mVideoHeight;
    } else if ( mVideoWidth * height > width * mVideoHeight ) {
     //Log.i("@@@", "image too tall, correcting");
     height = width * mVideoHeight / mVideoWidth;
    }
   } else if (widthSpecMode == MeasureSpec.EXACTLY) {
　　　　　　　　　......
   } else if (heightSpecMode == MeasureSpec.EXACTLY) {
　　　　　　　　　......
   } else {
　　　　　　　　　......
   }
  } else {
   // no size yet, just adopt the given spec sizes
  }
  setMeasuredDimension(width, height);
 }

@Override
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
　　　　 int width = getDefaultSize(0, widthMeasureSpec);
  int height = getDefaultSize(0, heightMeasureSpec);
  setMeasuredDimension(width, height);
 }