Android_GestureDetector手势滑动使用

Posted 杨迈1949

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Gesture在 ViewGroup中使用

GestureDetector类可以让我们快速的处理手势事件,如点击,滑动等。
使用GestureDetector分三步:
1. 定义GestureDetector类
2. 初始化手势类,同时设置手势监听
3. 将touch事件交给gesture处理

先来了解一下如何使用,后面会有示例:

package com.example.y2222.myview;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.widget.LinearLayout;

/**
 * Created by raise.yang on 2016/06/29.
 */
public class GestureDemoView extends LinearLayout {
    //1,定义GestureDetector类
    private GestureDetector m_gestureDetector;

    public GestureDemoView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public GestureDemoView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        //设置为可点击
        setClickable(true);
        //2,初始化手势类,同时设置手势监听
        m_gestureDetector = new GestureDetector(context, onGestureListener);
        //双击监听-一般很少用到
        m_gestureDetector.setOnDoubleTapListener(onDoubleTapListener);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //3,将touch事件交给gesture处理
        m_gestureDetector.onTouchEvent(event);
        return super.onTouchEvent(event);
    }

    //初始化手势监听对象,使用GestureDetector.OnGestureListener的实现抽象类,因为实际开发中好多方法用不上
    private final GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() {
        @Override
        public boolean onSingleTapUp(MotionEvent e) {
            Log.d("GestureDemoView", "onSingleTapUp() ");
            return super.onSingleTapUp(e);
        }

        @Override
        public void onLongPress(MotionEvent e) {
            Log.d("GestureDemoView", "onLongPress() ");
            super.onLongPress(e);
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            Log.d("GestureDemoView", "onScroll() distanceX = " + distanceX);
            return super.onScroll(e1, e2, distanceX, distanceY);
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            Log.d("GestureDemoView", "onFling() velocityX = " + velocityX);
            return super.onFling(e1, e2, velocityX, velocityY);
        }

        @Override
        public void onShowPress(MotionEvent e) {
            Log.d("GestureDemoView", "onShowPress() ");
            super.onShowPress(e);
        }

        @Override
        public boolean onDown(MotionEvent e) {
            Log.d("GestureDemoView", "onDown() ");
            return super.onDown(e);
        }

        @Override
        public boolean onDoubleTap(MotionEvent e) {
            Log.d("GestureDemoView", "onDoubleTap() ");
            return super.onDoubleTap(e);
        }

        @Override
        public boolean onDoubleTapEvent(MotionEvent e) {
            Log.d("GestureDemoView", "onDoubleTapEvent() ");
            return super.onDoubleTapEvent(e);
        }

        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            Log.d("GestureDemoView", "onSingleTapConfirmed() ");
            return super.onSingleTapConfirmed(e);
        }

        @Override
        public boolean onContextClick(MotionEvent e) {
            Log.d("GestureDemoView", "onContextClick() ");
            return super.onContextClick(e);
        }
    };
    private final GestureDetector.OnDoubleTapListener onDoubleTapListener = new GestureDetector.OnDoubleTapListener() {
        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            Log.d("GestureDemoView", "onSingleTapConfirmed() OnDoubleTapListener");
            return false;
        }

        @Override
        public boolean onDoubleTap(MotionEvent e) {
            Log.d("GestureDemoView", "onDoubleTap() OnDoubleTapListener");
            return false;
        }

        @Override
        public boolean onDoubleTapEvent(MotionEvent e) {
            Log.d("GestureDemoView", "onDoubleTapEvent() OnDoubleTapListener");
            return false;
        }
    };

}

注意:setClickable(true);一定要加,不然只会收到下例3个事件,被这个整了好长时间才找到原因.(⊙﹏⊙)b
这里写图片描述

对于单击,双击,拖动等事件调用见下图:
这里写图片描述
根据上图,每个方法大致都调用了,说明几个容易弄混的回调方法
1. onScroll()
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY)
e1:滑动事件的起点(也就是说onDown()的时候)
e2:当前滑动位置点(手指的位置)
distanceX:上次滑动(调用onScroll)到这次滑动的X轴的距离px,不是e1点到e2点的X轴的距离
distanceY:上次滑动(调用onScroll)到这次滑动的Y轴的距离px,不是e1点到e2点的Y轴的距离
2. onFling()
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
e1:拖动动事件的起点(也就是说onDown()的时候)
e2:onFling()调用时,手指的位置
velocityX:X轴上每秒滑动像素值
velocityY:Y轴上每秒滑动像素值
注意:,当拖动速率velocityX或velocityY超过ViewConfiguration.getMinimumFlingVelocity()最小拖动速率时,才会调用onFling(),也就是如果只拖动一点,或是慢慢的拖动,是不会触发该方法。
对应源码:

                if ((Math.abs(velocityY) > mMinimumFlingVelocity)
                        || (Math.abs(velocityX) > mMinimumFlingVelocity)){
                    handled = mListener.onFling(mCurrentDownEvent, ev, velocityX, velocityY);
                }

实践:使用GestureDetector实现左滑删除

在很多ListView中都有该效果,现在自己实现下,顺便熟悉GestureDetector的使用。
效果图:
这里写图片描述
GestureDemoView.java:

package com.example.y2222.myview;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.widget.LinearLayout;

import com.example.y2222.myapplication.R;

/**
 * Created by raise.yang on 2016/06/29.
 */
public class GestureDemoView extends LinearLayout {
    //1,定义GestureDetector类
    private GestureDetector m_gestureDetector;

    private int m_max_scrollX;

    public GestureDemoView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public GestureDemoView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        //设置为可点击
        setClickable(true);
        //2,初始化手势类,同时设置手势监听
        m_gestureDetector = new GestureDetector(context, onGestureListener);

        LayoutInflater.from(context).inflate(R.layout.view_gesture, this);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //3,将touch事件交给gesture处理
        m_gestureDetector.onTouchEvent(event);
        if (event.getAction() == MotionEvent.ACTION_UP) {
            // GestureDetector没有处理up事件的方法,只能在这里处理了。
            int scrollX = getScrollX();
            if (scrollX > m_max_scrollX / 2) {
                show_right_view();
            } else {
                hide_right_view();
            }
        }
        return super.onTouchEvent(event);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int childCount = getChildCount();
        for (int i = 0; i < childCount; i++) {
            //测量子view的宽高,?不测量,右侧布局会不显示,这里有点疑问
            measureChild(getChildAt(i), widthMeasureSpec, heightMeasureSpec);
            if (i == 1) {
                m_max_scrollX = getChildAt(i).getMeasuredWidth();
            }
        }
    }

    //初始化手势监听对象,使用GestureDetector.OnGestureListener的实现抽象类,因为实际开发中好多方法用不上
    private final GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() {

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            Log.d("GestureDemoView", "onScroll() distanceX = " + distanceX + " getScrollX = " + getScrollX() + " max_scrollX = " + m_max_scrollX);
            int scrollX = getScrollX();
            int minScrollX = -scrollX;
            int maxScrollY = m_max_scrollX - scrollX;
            // 对滑动的距离边界控制
            if (distanceX > maxScrollY) {
                distanceX = maxScrollY;
            } else if (distanceX < minScrollX) {
                distanceX = minScrollX;
            }
            scrollBy((int) distanceX, 0);
            return true;
        }

        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            Log.d("GestureDemoView", "onFling() velocityX = " + velocityX);
            if (velocityX < 0) {
                //快速向左滑动
                show_right_view();
            } else {
                hide_right_view();
            }
            return super.onFling(e1, e2, velocityX, velocityY);
        }
    };

    private void show_right_view() {
        scrollTo(m_max_scrollX, 0);
    }

    private void hide_right_view() {
        scrollTo(0, 0);
    }

}

view_gesture.xml

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:orientation="horizontal">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="左侧布局"/>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        >

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="收藏"/>

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="删除"/>
    </LinearLayout>
</merge>

xml文件中根标签使用<merge>,可减少一层view树嵌套,并且使用getChildCount()能得到我们想要的子view个数。

关于<merge>标签的使用,详见郭神的blog:http://blog.csdn.net/guolin_blog/article/details/43376527

实现也很简单,在scroll和fling的时候,得到滑动距离或滑动速度,再调用view自己的scrollTo()或scrollBy()滑动内部元素即可。
从效果图中,当滑动到一半松手时,立即滑动到最左边,完全没有动画,这样的体验很差,所以还需优化。关于滑动时增加动画效果,可以使用Scroller类完成,准备下期补上。

Gesture在 View中使用

和在viewgroup中一样,在view中,同样是经过三步来实现:
1. 定义GestureDetector类
2. 初始化手势类,同时设置手势监听
3. 将touch事件交给gesture处理
举个荔枝:
做了一个小球跟随手指移动的效果,先绘制小球,当手指放在小球上滑动时,会调用onScroll(),在这个方法中,修改圆心的位置进行重绘,这样小球就能移动了。
这里有2个难点:
1. 如何判断手指落在了小球上;
2. 滑动到边界时,不能超过边界;
效果图:
这里写图片描述
GestureView.java代码:

package com.example.y2222.myview;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;

/**
 * Created by raise.yang on 2016/07/05.
 */
public class GestureView extends View {

    private GestureDetector m_gestureDetector;
    private Paint m_paint;
    //小球的中心点
    private float centerX;
    private float centerY;
    //小球的半径
    private int radius;
    //是否touch在小球上
    private boolean touch_bool;

    public GestureView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public GestureView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        // 初始画笔
        m_paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        m_paint.setColor(getResources().getColor(android.R.color.holo_blue_light));
        //设置为可点击
        setClickable(true);
        //2,初始化手势类,同时设置手势监听
        m_gestureDetector = new GestureDetector(context, onGestureListener);
        radius = 50;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //3,将touch事件交给gesture处理
        m_gestureDetector.onTouchEvent(event);
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            //判断手指落在了小球上
            if (getDistanceByPoint((int) centerX, (int) centerY, (int) event.getX(), (int) event.getY()) < radius) {
                touch_bool = true;
            } else {
                touch_bool = false;
            }
        }
        return super.onTouchEvent(event);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        // 默认圆心在中心点
        if (w > 0) {
            centerX = w / 2;
        }
        if (h > 0) {
            centerY = h / 2;
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawCircle(centerX, centerY, radius, m_paint);
    }

    GestureDetector.OnGestureListener onGestureListener = new GestureDetector.SimpleOnGestureListener() {
        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            if (touch_bool) {
                centerY -= distanceY;
                centerX -= distanceX;
                //处理边界问题
                if (centerX < radius) {
                    centerX = radius;
                } else if (centerX > getWidth() - radius) {
                    centerX = getWidth() - radius;
                }
                if (centerY < radius) {
                    centerY = radius;
                } else if (centerY > getHeight() - radius) {
                    centerY = getHeight() - radius;
                }
                //修改圆心后,通知重绘
                postInvalidate();
            }
            return true;
        }
    };

    /**
     * 计算两点间的距离
     */
    private int getDistanceByPoint(int x1, int y1, int x2, int y2) {
        double temp = Math.abs((x2 - x1) * (x2 - x1) - (y2 - y1) * (y2 - y1));
        return (int) Math.sqrt(temp);
    }

}

在处理问题1时,我设置了一个boolean值,在用户触摸的时候去判断,当前点和圆心点的距离是否小于半径,若小于,说明在圆内。这样在滑动的时候,就去判断一下,是否需要滑动小球。
控制边界,其实就是控制圆心点的坐标,只要保证落在(radius,radius),(getWidth()-radius,getHeight()-radius)两点矩形中即可。

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