Android下图片或按钮等可拖动到任意位置的效果实现源码

Android下图片可拖动到任意位置的效果
下面为Activity的代码：

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public class DraftTest extends Activity {
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/** Called when the activity is first created. */
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@Override
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public void onCreate(Bundle savedInstanceState) {
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super.onCreate(savedInstanceState);
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setContentView(R.layout.sign);
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DisplayMetrics dm = getResources().getDisplayMetrics();
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final int screenWidth = dm.widthPixels;
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final int screenHeight = dm.heightPixels - 50;
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//拖动的按钮
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final Button b=(Button)findViewById(R.id.startBtn);
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//添加触摸事件
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b.setOnTouchListener(new OnTouchListener(){
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   int lastX, lastY; //记录移动的最后的位置
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   public boolean onTouch(View v, MotionEvent event) {
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    //获取Action
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    int ea=event.getAction();
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    Log.i("TAG", "Touch:"+ea);
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    switch(ea){
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    case MotionEvent.ACTION_DOWN:   //按下
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     lastX = (int) event.getRawX();
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     lastY = (int) event.getRawY();
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     break;
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     /**
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      * layout(l,t,r,b)
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      * l Left position, relative to parent
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                    t Top position, relative to parent
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                    r Right position, relative to parent
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                    b Bottom position, relative to parent
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      * */
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    case MotionEvent.ACTION_MOVE: //移动
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     //移动中动态设置位置
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     int dx =(int)event.getRawX() - lastX;
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     int dy =(int)event.getRawY() - lastY;
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     int left = v.getLeft() + dx;
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     int top = v.getTop() + dy;
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     int right = v.getRight() + dx;
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     int bottom = v.getBottom() + dy;
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     if(left < 0){
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      left = 0;
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      right = left + v.getWidth();
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     }
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     if(right > screenWidth){
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      right = screenWidth;
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      left = right - v.getWidth();
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     }
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     if(top < 0){
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      top = 0;
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      bottom = top + v.getHeight();
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     }
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     if(bottom > screenHeight){
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      bottom = screenHeight;
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      top = bottom - v.getHeight();
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     }
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     v.layout(left, top, right, bottom);
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     Log.i("", "position：" + left +", " + top + ", " + right + ", " + bottom);
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     //将当前的位置再次设置
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     lastX = (int) event.getRawX();
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     lastY = (int) event.getRawY();
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     break;
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    case MotionEvent.ACTION_UP:   //脱离
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     break;
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    }
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    return false;
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   }});
70     www.zzzyk.com
}
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}
XML配置文件Sign.xml的代码:

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<?xml version="1.0" encoding="utf-8"?>
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
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android:id="@+id/layoutRacingNeedForSpeed" android:padding="0px"
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android:layout_width="fill_parent" android:layout_height="fill_parent">
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<Button
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android:id="@+id/startBtn"
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android:text="tuodongdeanniu"
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android:layout_centerInParent="true"
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android:layout_width="wrap_content" android:layout_height="wrap_content"/>
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</RelativeLayout>
作者：Jimmy_牛牛

补充：移动开发 , Android ,