Touch事件--对GestureDetector的理解

来源：互联网发布：云计算平台技术架构编辑：程序博客网时间：2024/06/15 18:50

作用

简单来说，GestureDetector对View触摸事件的封装。它是触摸事件的帮助类。

我们知道通过重新复写View/ViewGroup的dispatchTouchEvent方法，可以定义View对触摸事件的处理。但是，如果我们根据这些事件完成对一个View的双击、滑动（fling）等触摸操作，还是比较困难的。因为我们要写很多关于算法类的东西。而使用GestureDetector，就会省事很多，我们可以只处理我们关心的事件。例如：doubleClick，press等。而不用识别用户的TouchEvent。

用法

1. 构造GestureDetector。GestureDetector构造函数一定要传OnGestureListener传监听器，他包装了down、press、longPress、sigleTapUp、scroll、fling等事件。另外我们也可以在GestureDetector设置 setOnDoubleTapListener对双击事件的监听，通过setContextClickListener设置对单击事件的监听。推荐使用GestureDetector.SimpleOnGestureListener适配器实现。可减少代码的编写。

注意：当我们对一些手势关心时（需要处理的手势），要在返回值设为true.

2. 将事件交给GestureDetector处理。我们可以通过自定义View，或者给View设置onTouchListener实现。是通过将event事件传递给gestureDet.onTouchEvent(event);实现的。

        view.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View v, MotionEvent event) {                gestureDet.onTouchEvent(event);                return true;            }        });

完整代码

package com.tiandh.tdhtest01;import android.os.Bundle;import android.support.annotation.Nullable;import android.support.v7.app.AppCompatActivity;import android.util.Log;import android.view.GestureDetector;import android.view.MotionEvent;import android.view.View;import android.widget.Button;import android.widget.LinearLayout;import com.tiandh.tdhtest01.view.MoveRelativeLayout;/** * Created by Administrator on 2017/5/15 0015. */public class TestScroller extends AppCompatActivity implements View.OnClickListener {    private Button buttonSelf;    private LinearLayout llScroller;    private MoveRelativeLayout viewParent;    private View moveView;    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_test_scroller);        buttonSelf = (Button) findViewById(R.id.bt_scroll_self);        llScroller = (LinearLayout) findViewById(R.id.ll_scroller);        findViewById(R.id.bt_scroll_self).setOnClickListener(this);        findViewById(R.id.bt_scroll_parent).setOnClickListener(this);        initGestureTest();    }    private GestureDetector.OnGestureListener gestureListener = new GestureDetector.SimpleOnGestureListener() {        @Override        public boolean onDown(MotionEvent e) {            Log.i("tag", "onDown--");            return true;        }        @Override        public void onShowPress(MotionEvent e) {            Log.i("tag", "onPress--");            return true;        }        @Override        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {            Log.i("tag", "e1.getX=" + e1.getX() + ", e1.getY=" + e1.getY() + ", e2.getX=" + e2.getX() + ", e2.getY=" + e2.getY());            viewParent.scrollTo((int) -e2.getX(), (int) -e2.getY());            return true;        }        @Override        public void onLongPress(MotionEvent e) {            Log.i("tag", "onLongPress--");            return true;        }        @Override        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {            Log.i("tag", "onFling e1.getX=" + e1.getX() + ", e2.getX=" + e2.getX() + ", vx=" + velocityX + ", vy=" + velocityY);            viewParent.fling((int) -e2.getX(), (int) -e2.getY(), (int) -velocityX, (int) -velocityY);            return true;        }    };    private void initGestureTest() {        viewParent = (MoveRelativeLayout) findViewById(R.id.rl_content);        final GestureDetector gestureDet = new GestureDetector(this, gestureListener);        viewParent.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View v, MotionEvent event) {                return gestureDet.onTouchEvent(event);            }        });        moveView = findViewById(R.id.view_move);    }    int i;    @Override    public void onClick(View v) {        //注意view的scrollTo,scrollBy是view里面内容滑动        switch (v.getId()) {            case R.id.bt_scroll_self:                if (i++ % 2 == 1) {                    buttonSelf.scrollTo(60, 0);                } else {                    buttonSelf.scrollTo(0, 0);                }                break;            case R.id.bt_scroll_parent:                if (i++ % 2 == 1) {                    llScroller.scrollTo(60, 0);                } else {                    llScroller.scrollTo(0, 0);                }                break;        }    }}

MoveRelativeLayout.java

package com.tiandh.tdhtest01.view;import android.content.Context;import android.os.Handler;import android.util.AttributeSet;import android.util.Log;import android.widget.RelativeLayout;import android.widget.Scroller;/** * Created by Administrator on 2017/5/15 0015. */public class MoveRelativeLayout extends RelativeLayout {    private Scroller scroller;    private Handler mHander;    public MoveRelativeLayout(Context context) {        this(context, null);    }    public MoveRelativeLayout(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public MoveRelativeLayout(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        scroller = new Scroller(context);        mHander = new Handler();    }    public void fling( int startX, int startY, int velocityX, int velocityY  ) {        scroller.fling(startX, startY, velocityX, velocityY, -getWidth(), getWidth(), -getHeight(), getHeight());        startFling();    }    private void startFling() {        Log.i("tag", "srcoller X="+getScrollX());        if(scroller.computeScrollOffset()){            scrollTo(scroller.getCurrX(), scroller.getCurrY());            mHander.postDelayed(new Runnable() {                @Override                public void run() {                    startFling();                }            }, 50);        }    }}

activity_test_scroller.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:id="@+id/ll_scroller"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <Button        android:id="@+id/bt_scroll_self"        android:layout_width="180dp"        android:layout_height="40dp"        android:layout_marginLeft="40dp"        android:layout_marginTop="40dp"        android:text="滑动Button按钮" />    <Button        android:id="@+id/bt_scroll_parent"        android:layout_width="180dp"        android:layout_height="40dp"        android:layout_marginLeft="40dp"        android:text="滑动Layout按钮" />    <com.tiandh.tdhtest01.view.MoveRelativeLayout        android:id="@+id/rl_content"        android:layout_width="match_parent"        android:layout_height="0dp"        android:layout_weight="1"        android:background="#33333333">        <View            android:id="@+id/view_move"            android:layout_width="30dp"            android:layout_height="30dp"            android:background="#aaff00" />    </com.tiandh.tdhtest01.view.MoveRelativeLayout></LinearLayout>

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