Android视频播放器屏幕左侧边随手指上下滑动亮度调节功能的原理实现

import android.app.Activity;  import android.os.Bundle;  import android.view.LayoutInflater;  import android.view.MotionEvent;  import android.view.View;  import android.view.WindowManager;  import android.widget.TextView;  public class MainActivity extends Activity {    private float startY = 0;//手指按下时的Y坐标    private float startX = 0;//手指按下时的Y坐标    private TextView brightnessTextView;    private View mVideoView;    @Override    protected void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);      mVideoView = LayoutInflater.from(this).inflate(R.layout.activity_main, null);      setContentView(mVideoView);      brightnessTextView = (TextView) mVideoView.findViewById(R.id.text);    }    /*   * 设置屏幕亮度   * 0 最暗   * 1 最亮   */    public void setBrightness(float brightness) {      WindowManager.LayoutParams lp = getWindow().getAttributes();      lp.screenBrightness = lp.screenBrightness + brightness / 255.0f;      if (lp.screenBrightness > 1) {        lp.screenBrightness = 1;      } else if (lp.screenBrightness < 0.1) {        lp.screenBrightness = (float) 0.1;      }      getWindow().setAttributes(lp);      float sb = lp.screenBrightness;      brightnessTextView.setText((int) Math.ceil(sb * 100) + "%");    }    @Override    public boolean onTouchEvent(MotionEvent event) {      int screenWidth = mVideoView.getWidth();      switch (event.getAction()) {        case MotionEvent.ACTION_DOWN:          startX = event.getX();          startY = event.getY();          break;        case MotionEvent.ACTION_MOVE:          float endY = event.getY();          float distanceY = startY - endY;          if (startX > screenWidth / 2) {            //右边            //在这里处理音量          } else {            //屏幕左半部分上滑，亮度变大，下滑，亮度变小            final double FLING_MIN_DISTANCE = 0.5;            final double FLING_MIN_VELOCITY = 0.5;            if (distanceY > FLING_MIN_DISTANCE && Math.abs(distanceY) > FLING_MIN_VELOCITY) {              setBrightness(10);            }            if (distanceY < FLING_MIN_DISTANCE && Math.abs(distanceY) > FLING_MIN_VELOCITY) {              setBrightness(-10);            }          }          break;      }      return super.onTouchEvent(event);    }  }  

<?xml version="1.0" encoding="utf-8"?>  <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/activity_main"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:background="@mipmap/ic_launcher">      <TextView      android:id="@+id/text"      android:layout_width="150dp"      android:layout_height="50dp"      android:layout_gravity="center"      android:background="@android:color/holo_orange_light"      android:gravity="center"      android:textColor="@android:color/white" />  </FrameLayout>