本文主要是介绍Touch事件--对GestureDetector的理解，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
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() {@Overridepublic 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;@Overrideprotected 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() {@Overridepublic boolean onDown(MotionEvent e) {Log.i("tag", "onDown--");return true;}@Overridepublic void onShowPress(MotionEvent e) {Log.i("tag", "onPress--");return true;}@Overridepublic 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;}@Overridepublic void onLongPress(MotionEvent e) {Log.i("tag", "onLongPress--");return true;}@Overridepublic 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() {@Overridepublic boolean onTouch(View v, MotionEvent event) {return gestureDet.onTouchEvent(event);}});moveView = findViewById(R.id.view_move);}int i;@Overridepublic 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() {@Overridepublic 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"><Buttonandroid: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" /><Buttonandroid: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.MoveRelativeLayoutandroid:id="@+id/rl_content"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"android:background="#33333333"><Viewandroid: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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