Android移动开发-Android屏幕手势检测的实现

Android屏幕手势检测的原理是由于触摸事件的检测与识别比较繁琐，因此Android提供了手势检测器帮助开发者识别手势。利用手势检测器可以自动辨别常用的几个手势事件，如点击、长按、滑动等，从而使开发者专注于业务逻辑，不必在手势的行为判断上绞尽脑汁。

• layout/activity_gesture_detector.xml界面布局代码如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingTop="10dp">

    <TextView
        android:id="@+id/tv_gesture"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="这里查看手势结果"
        android:textColor="@color/black"
        android:textSize="17sp" />

</LinearLayout>

• GestureDetectorActivity.java逻辑代码如下：

package com.fukaimei.gesturedetector;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.TextView;

import com.fukaimei.gesturedetector.util.DateUtil;

public class GestureDetectorActivity extends AppCompatActivity {
    private TextView tv_gesture;
    private GestureDetector mGesture;
    private String desc = "";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_gesture_detector);
        tv_gesture = (TextView) findViewById(R.id.tv_gesture);
        mGesture = new GestureDetector(this, new MyGestureListener());
    }

    public boolean dispatchTouchEvent(MotionEvent event) {
        mGesture.onTouchEvent(event);
        return true;
    }

    final class MyGestureListener implements GestureDetector.OnGestureListener {

        @Override
        public final boolean onDown(MotionEvent event) {
//          desc = String.format("%s%s 您按下来了\n", desc, DateUtil.getNowTime());
//          tv_gesture.setText(desc);
            //onDown的返回值没有作用，不影响其它手势的处理
            return true;
        }

        @Override
        public final boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            float offsetX = e1.getX() - e2.getX();
            float offsetY = e1.getY() - e2.getY();
            if (Math.abs(offsetX) > Math.abs(offsetY)) {
                if (offsetX > 0) {
                    desc = String.format("%s%s 您向左滑动了一下\n", desc, DateUtil.getNowTime());
                } else {
                    desc = String.format("%s%s 您向右滑动了一下\n", desc, DateUtil.getNowTime());
                }
            } else {
                if (offsetY > 0) {
                    desc = String.format("%s%s 您向上滑动了一下\n", desc, DateUtil.getNowTime());
                } else {
                    desc = String.format("%s%s 您向下滑动了一下\n", desc, DateUtil.getNowTime());
                }
            }
            tv_gesture.setText(desc);
            return true;
        }

        @Override
        public final void onLongPress(MotionEvent event) {
            desc = String.format("%s%s 您长按了一下下\n", desc, DateUtil.getNowTime());
            tv_gesture.setText(desc);
        }

        @Override
        public final boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            return false;
        }

        @Override
        public final void onShowPress(MotionEvent event) {
        }

        @Override
        public boolean onSingleTapUp(MotionEvent event) {
            desc = String.format("%s%s 您轻轻点了一下\n", desc, DateUtil.getNowTime());
            tv_gesture.setText(desc);
            //返回true表示我已经处理了，别处不要再处理这个手势
            return true;
        }

    }

}

• Demo程序运行效果界面截图如下：

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