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

package zhangphil.app;

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>