Android拖動控制項改變其位置

mainActivity如下:

package cn.dragtest;import android.app.Activity;import android.graphics.Rect;import android.os.Bundle;import android.util.DisplayMetrics;import android.view.MotionEvent;import android.view.View;import android.view.View.OnTouchListener;import android.view.Window;import android.widget.Button;import android.widget.ImageView;public class MainActivity extends Activity implements OnTouchListener{   private Button mButton;   private ImageView mImageView;   private DisplayMetrics displayMetrics;   private float lastX=0;   private float lastY=0;   private int screenWidth=0;   private int screenHeight=0;   private int left;   private int top;   private int right;   private int bottom;   private boolean isFirst=true;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        initView();    }private void initView() {         mButton=(Button) findViewById(R.id.button);         mImageView=(ImageView) findViewById(R.id.imageView);         mButton.setOnTouchListener(this);         mImageView.setOnTouchListener(this);}public boolean onTouch(View view, MotionEvent event) {if (isFirst) {// 得到螢幕的寬displayMetrics = getResources().getDisplayMetrics();screenWidth = displayMetrics.widthPixels;// 得到標題列和狀態列的高度Rect rect = new Rect();Window window = getWindow();mImageView.getWindowVisibleDisplayFrame(rect);int statusBarHeight = rect.top;int contentViewTop = window.findViewById(Window.ID_ANDROID_CONTENT).getTop();int titleBarHeight = contentViewTop - statusBarHeight;// 得到螢幕的高screenHeight = displayMetrics.heightPixels- (statusBarHeight + titleBarHeight);isFirst=false;}int action=event.getAction();switch (action) {//按下case MotionEvent.ACTION_DOWN://按下處座標lastX=event.getRawX();lastY=event.getRawY();break;//移動case MotionEvent.ACTION_MOVE://移動的距離float distanceX=event.getRawX()-lastX;float distanceY=event.getRawY()-lastY;//移動後控制項的座標left=(int)(view.getLeft()+distanceX);top=(int)(view.getTop()+distanceY);right=(int)(view.getRight()+distanceX);bottom=(int)(view.getBottom()+distanceY);//處理拖出螢幕的情況if (left<0) {left=0;right=view.getWidth();}if (right>screenWidth) {right=screenWidth;left=screenWidth-view.getWidth();}if (top<0) {top=0;bottom=view.getHeight();}if (bottom>screenHeight) {bottom=screenHeight;top=screenHeight-view.getHeight();}//顯示圖片view.layout(left, top, right, bottom);lastX=event.getRawX();lastY=event.getRawY();break;//抬起case MotionEvent.ACTION_UP:break;default:break;}return false;}}

main.xml如下:

<LinearLayout     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"    android:orientation="vertical"    android:gravity="center_horizontal"     >    <ImageView        android:id="@+id/imageView"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:src="@drawable/ic_launcher"        android:clickable="true"     />    <Button         android:id="@+id/button"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="please drag"        android:clickable="true"    /></LinearLayout>