Android觸控事件

標籤：

觸控事件
MotionEvent類：

    //單擊觸摸按下動作   public static final int ACTION_DOWN             = 0;    /**     * Constant for {@link #getActionMasked}: A pressed gesture has finished, the     * motion contains the final release location as well as any intermediate     * points since the last down or move event.     * 單擊觸摸離開動作     */    public static final int ACTION_UP               = 1;    /**     * Constant for {@link #getActionMasked}: A change has happened during a     * press gesture (between {@link #ACTION_DOWN} and {@link #ACTION_UP}).     * The motion contains the most recent point, as well as any intermediate     * points since the last down or move event.     * 觸摸點移動動作     */    public static final int ACTION_MOVE             = 2;    /**     * Constant for {@link #getActionMasked}: The current gesture has been aborted.     * You will not receive any more points in it.  You should treat this as     * an up event, but not perform any action that you normally would.     * 觸摸動作取消     */    public static final int ACTION_CANCEL           = 3;    /**     * Constant for {@link #getActionMasked}: A movement has happened outside of the     * normal bounds of the UI element.  This does not provide a full gesture,     * but only the initial location of the movement/touch.     * 觸摸動作超出邊界     */    public static final int ACTION_OUTSIDE          = 4;    /**     * Constant for {@link #getActionMasked}: A non-primary pointer has gone down.     * <p>     * Use {@link #getActionIndex} to retrieve the index of the pointer that changed.     * </p><p>     * The index is encoded in the {@link #ACTION_POINTER_INDEX_MASK} bits of the     * unmasked action returned by {@link #getAction}.     * </p>     * 多點觸摸按下動作     */    public static final int ACTION_POINTER_DOWN     = 5;    /**     * Constant for {@link #getActionMasked}: A non-primary pointer has gone up.     * <p>     * Use {@link #getActionIndex} to retrieve the index of the pointer that changed.     * </p><p>     * The index is encoded in the {@link #ACTION_POINTER_INDEX_MASK} bits of the     * unmasked action returned by {@link #getAction}.     * </p>     * 多點離開動作     */    public static final int ACTION_POINTER_UP       = 6;

MotionEvent提供的方法：

getTop():擷取到的是View自身的頂邊到其父布局頂邊的距離。getLeft():擷取到的是View自身的左邊到其父布局左邊的距離。getRight():擷取到的是View自身的右邊到其父布局右邊的距離。getBottom():擷取到的是View自身的底邊到其父布局底邊的距離。getX():擷取點擊事件距離控制項左邊的距離getY():擷取點擊事件距離控制項頂邊的距離getRawX():擷取點擊事距離整個螢幕左邊的距離，即絕對座標。getRawY():擷取點擊事距離整個螢幕頂邊的距離，即絕對座標。

**實現滑動的基本原理（核心思想）：
當觸摸View時候，系統記錄當前觸摸點的座標，當手指移動時候，系統記錄下移動的觸摸點座標，從而擷取到相對於前一次座標點的位移量，並且通過位移量修改view的座標，這樣不斷重複，從而實現滑動效果。**
實現滑動的常用方法：
layout方法：

package com.example.drawdemo;import android.content.Context;import android.graphics.Color;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;public class MyView5 extends View {    private int lastX;    private int lastY;    public MyView5(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        initView();    }    public MyView5(Context context, AttributeSet attrs) {        super(context, attrs);        initView();    }    public MyView5(Context context) {        super(context);        initView();    }    private void initView() {        setBackgroundColor(Color.BLUE);    }    // 視圖座標方式    public boolean onTouchEvent(MotionEvent event) {        int x = (int) event.getX();        int y = (int) event.getY();        switch (event.getAction()) {        case MotionEvent.ACTION_DOWN:            lastX = x;            lastY = y;            break;        case MotionEvent.ACTION_MOVE:            // 計算位移量            int offsetX = x - lastX;            int offsetY = y - lastY;            layout(getLeft() + offsetX, getTop() + offsetY, getRight() + offsetX, getBottom() + offsetY);            break;        default:            break;        }        return true;    }}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.example.drawdemo.MainActivity" >    <com.example.drawdemo.MyView5        android:layout_width="100dp"        android:layout_height="100dp" /></RelativeLayout>

通過LayoutParams進行滑動。
LayoutParams 儲存了一個View的布局參數，因此在程式中，通過改變LayoutParams修改一個布局的位置參數，從而達到改變View位置的效果。

而且我們可以使用getLayoutparams()來擷取一個View的LayoutParams.計算位移量的方法與在Layout方法中計算offset也是一樣的，當擷取位移量後，就可以通過setLayoutParams來改變Layoutparams.

當然擷取父容易布局，會有不同的布局（如果父容易是LinearLatyou，那麼就要使用LinearLayout.LayoutParams.如果是RelativeLayout,那麼就要使用RelativeLayout.LayoutParams.），所以我們直接使用ViewGroup.MarginLayoutParams來實現這個功能。

                    ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams) getLayoutParams();// LinearLayout.LayoutParams layoutParams =(LinearLayout.LayoutParams) getLayoutParams();                    layoutParams.leftMargin = getLeft() + offsetX;                    layoutParams.topMargin = getTop() + offsetY;

這個使用更加方便，不用考錄父容器布局。

package com.example.drawdemo;import android.content.Context;import android.graphics.Color;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import android.view.ViewGroup;public class MyView6 extends View {    private int lastX;    private int lastY;    public MyView6(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        // TODO Auto-generated constructor stub        ininView();    }    public MyView6(Context context, AttributeSet attrs) {        super(context, attrs);        ininView();        // TODO Auto-generated constructor stub    }    public MyView6(Context context) {        super(context);        ininView();        // TODO Auto-generated constructor stub    }    private void ininView() {         setBackgroundColor(Color.GREEN);    }       @Override        public boolean onTouchEvent(MotionEvent event) {            int x = (int) event.getX();            int y = (int) event.getY();            switch (event.getAction()) {                case MotionEvent.ACTION_DOWN:                    // 記錄觸摸點座標                    lastX = (int) event.getX();                    lastY = (int) event.getY();                    break;                case MotionEvent.ACTION_MOVE:                    // 計算位移量                    int offsetX = x - lastX;                    int offsetY = y - lastY;                    ViewGroup.MarginLayoutParams layoutParams = (ViewGroup.MarginLayoutParams) getLayoutParams();//                  LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams) getLayoutParams();                    layoutParams.leftMargin = getLeft() + offsetX;                    layoutParams.topMargin = getTop() + offsetY;                    setLayoutParams(layoutParams);                    break;            }            return true;        }}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.example.drawdemo.MainActivity" >    <com.example.drawdemo.MyView6        android:layout_width="100dp"        android:layout_height="100dp" /></RelativeLayout>

通過scrollTo與scorllBy進行滑動。
android 系統提供這個兩個方式進行改變一個View的位置
與前面的方法相同，也是計算位移量。

package com.example.drawdemo;import android.content.Context;import android.graphics.Color;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;public class MyView7 extends View{    private int lastX;    private int lastY;    public MyView7(Context context) {        super(context);        ininView();    }    public MyView7(Context context, AttributeSet attrs) {        super(context, attrs);        ininView();    }    public MyView7(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        ininView();    }    private void ininView() {        setBackgroundColor(Color.YELLOW);    }    @Override    public boolean onTouchEvent(MotionEvent event) {        int x = (int) event.getX();        int y = (int) event.getY();        switch (event.getAction()) {            case MotionEvent.ACTION_DOWN:                lastX = (int) event.getX();                lastY = (int) event.getY();                break;            case MotionEvent.ACTION_MOVE:                int offsetX = x - lastX;                int offsetY = y - lastY;                ((View) getParent()).scrollBy(-offsetX, -offsetY);                break;        }        return true;    }}

Android觸控事件