Android-在应用中使用拖拽教程

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

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目录

1. 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
2. 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

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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

也创建下面的shape——droptarget.xml文件

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

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);

@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;
}
  }
} 

如果你开启这个activity，你应该能够拖动ImageView到其他容

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