Android-在应用中使用拖拽教程

Lars Vogel

Version 1.3
Copyright © 2012-2014 vogella GmbH
21.11.2014
在Android中使用拖拽

这个教程描述在Android中如何使用拖拽

Android拖拽
1.1在Android中使用拖拽
1.2允许view拖拽
1.3定义拖动目标
练习：拖拽
2.1这个练习的目标
2.2创建项目
2.3创建 xml Drawable
2.4Activity和layout

1.Android拖拽

1.1在Android中使用拖拽
Android4.0支持在view或viewGroup上的拖拽view
1.2允许view拖拉
你注册一个onTouchListener或LongClickListener在被拖拽的view上使其能够拖拽
View的startDrag方法开始一个拖拽操作。在这个方法你也可以通过ClipData的实例指定按下拖拽目标数据
你也可以通过DragShadowBuilder实例的startDrag方法。这个对象指定图像用于拖拽操作。例如你可以直接地通过View，在拖拽操作中展现一个view的图像
下面的例子演示在TouchListener下的拖拉操作设置

    // Assign the touch listener to your view which you want to move            findViewById(R.id.myimage1).setOnTouchListener(new MyTouchListener());    // This defines your touch listener    private final class MyTouchListener implements OnTouchListener {      public boolean onTouch(View view, MotionEvent motionEvent) {if (motionEvent.getAction() == MotionEvent.ACTION_DOWN) {  ClipData data = ClipData.newPlainText("", "");  DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);  view.startDrag(data, shadowBuilder, view, 0);  view.setVisibility(View.INVISIBLE);  return true;} else {return false;}     }    }

1.3 定义拖拉目标

能够拖拽的view得到一个onDragListener分配的实例。在这个拖拽监听，你接收预定义的拖拽相关事件回调

DragEvent.ACTION_DRAG_STARTED
DragEvent.ACTION_DRAG_ENTERED
DragEvent.ACTION_DRAG_EXITED
DragEvent.ACTION_DROP

DragEvent.ACTION_DRAG_ENDED
一个有onDragListener的view是可以拖拽的区域，通过setonDragListener得到一个分配onDragListener

 findViewById(R.id.bottomright).setOnDragListener(new MyDragListener());class MyDragListener implements OnDragListener {  Drawable enterShape = getResources().getDrawable(R.drawable.shape_droptarget);  Drawable normalShape = getResources().getDrawable(R.drawable.shape);  @Override  public boolean onDrag(View v, DragEvent event) {    int action = event.getAction();    switch (event.getAction()) {    case DragEvent.ACTION_DRAG_STARTED:// do nothing  break;  case DragEvent.ACTION_DRAG_ENTERED:    v.setBackgroundDrawable(enterShape);    break;  case DragEvent.ACTION_DRAG_EXITED:            v.setBackgroundDrawable(normalShape);    break;  case DragEvent.ACTION_DROP:    // Dropped, reassign View to ViewGroup    View view = (View) event.getLocalState();            ViewGroup owner = (ViewGroup) view.getParent();    owner.removeView(view);    LinearLayout container = (LinearLayout) v;    container.addView(view);    view.setVisibility(View.VISIBLE);    break;  case DragEvent.ACTION_DRAG_ENDED:    v.setBackgroundDrawable(normalShape);    default:    break;  }  return true;}}

练习：拖拽

2.1练习目标
在这个练习中，你创建多个允许他们之间拖动views的Viewgroup
2.2创建项目
创建一个新的名为com.vogella.android.draganddrop的Android 项目和一个叫DragActivity的Activity
创建 XMLDrawables
在这个练习你能够使用 XML Drawable
在这个部分你在res/drawable文件夹创建多个XML Drawable
创建下面shape.xml文件在这个文件夹

    <?xml version="1.0" encoding="UTF-8"?>

也创建下面的shape——droptarget.xml文件

<?xml version="1.0" encoding="UTF-8"?>

2.4Activity和layout
用下面的代码的修改Activity的layout

        <?xml version="1.0" encoding="utf-8"?>

用下面的代码修改你的activity

        package com.vogella.android.draganddrop;import android.app.Activity;import android.content.ClipData;import android.graphics.drawable.Drawable;import android.os.Bundle;import android.view.DragEvent;import android.view.MotionEvent;import android.view.View;import android.view.View.DragShadowBuilder;import android.view.View.OnDragListener;import android.view.View.OnTouchListener;import android.view.ViewGroup;import android.widget.LinearLayout;public class DragActivity extends Activity {/** Called when the activity is first created. */  @Override  public void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.main);    findViewById(R.id.myimage1).setOnTouchListener(new MyTouchListener());    findViewById(R.id.myimage2).setOnTouchListener(new MyTouchListener());    findViewById(R.id.myimage3).setOnTouchListener(new MyTouchListener());    findViewById(R.id.myimage4).setOnTouchListener(new MyTouchListener());    findViewById(R.id.topleft).setOnDragListener(new MyDragListener());    findViewById(R.id.topright).setOnDragListener(new MyDragListener());    findViewById(R.id.bottomleft).setOnDragListener(new MyDragListener());    findViewById(R.id.bottomright).setOnDragListener(new MyDragListener());  }  private final class MyTouchListener implements OnTouchListener {    public boolean onTouch(View view, MotionEvent motionEvent) {      if (motionEvent.getAction() == MotionEvent.ACTION_DOWN) {        ClipData data = ClipData.newPlainText("", "");        DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);        view.startDrag(data, shadowBuilder, view, 0);        view.setVisibility(View.INVISIBLE);        return true;      } else {        return false;      }    }  }  class MyDragListener implements OnDragListener {    Drawable enterShape = getResources().getDrawable(R.drawable.shape_droptarget);    Drawable normalShape = getResources().getDrawable(R.drawable.shape);@Overridepublic boolean onDrag(View v, DragEvent event) {  int action = event.getAction();  switch (event.getAction()) {  case DragEvent.ACTION_DRAG_STARTED:    // do nothing    break;  case DragEvent.ACTION_DRAG_ENTERED:    v.setBackgroundDrawable(enterShape);    break;  case DragEvent.ACTION_DRAG_EXITED:    v.setBackgroundDrawable(normalShape);    break;  case DragEvent.ACTION_DROP:    // Dropped, reassign View to ViewGroup    View view = (View) event.getLocalState();    ViewGroup owner = (ViewGroup) view.getParent();    owner.removeView(view);    LinearLayout container = (LinearLayout) v;    container.addView(view);    view.setVisibility(View.VISIBLE);    break;  case DragEvent.ACTION_DRAG_ENDED:    v.setBackgroundDrawable(normalShape);  default:    break;  }  return true;}  }}

如果你开启这个activity，你应该能够拖动ImageView到其他容

原文地址

Android-在应用中使用拖拽教程