Android视频播放器屏幕左侧边随手指上下滑动亮度调节变暗变亮原理实现

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);      }  }  
activity_main.xml布局文件：
<?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>