Android setTag()与getTag(),与set多个setTag()

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首先我们要知道setTag方法是干什么的,SDK解释为

Tags

Unlike IDs, tags are not used to identify views. Tags are essentially an extra piece of information that can be associated with a view. They are most often used as a convenience to store data related to views in the views themselves rather than by putting them in a separate structure.

 

Tag不像ID是用标示view的。

Tag从本质上来讲是就是相关联的view的额外的信息。

它们经经常使用来存储一些view的数据。这样做很方便而不用存入另外的单独结构。

 Tag有一个特点,绑定数据到指定控件(view),而不显示出来。

setTagandroidview类中非常实用的一个方法,

与setId()不同。findViewById找到的是对象本身。

而setTag(),取出来的是对象所指向的对象。



在同一个类中,存取数据非常方便,不用数据库建库,

也比sharePreference更节约内存。

setTagObject tag)方法比較简单 


比方

TextView tvExecutor = (TextView)findViewById(R.id.t);

tvExecutor.setTag(selectedUserMap);


这个selectedUserMap 

能够使Map<String, String> selectedUserMap这个对象。

也能够是LinkedList<CarEntity> mList 这个对象。

       能够存储各种暂时数据,可是还不能称其为存储方式。

      在开发中,我们能够使用setTag(),getTag(),存取数据。

      可不能够一个对象。设置多个Tag呢?答案是肯定的


在res/values/strings.xml中加入
<span face="Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif" style="font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif;"><span style="line-height: 18px;"><span style="color:#cc0000;"><resources></span></span></span>
<span style="color:#cc0000;"><span face="Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif" style="font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif;"><item type="id" name="tag_a</span><span style="font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif; background-color: rgb(240, 240, 240);">"></item></span></span>
<span face="Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif" style="font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif;"><span style="color:#cc0000;"><item type="id" name="tag_b"></item></span></span>
<span face="Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif" style="font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif;"><span style="color:#cc0000;"></resources></span></span>
<span face="Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif" style="font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif;">
</span>
在activity中,使用的时候写成
<span face="Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif" style="font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif;"></span>
<code style="border: 0px; vertical-align: baseline; background-color: rgb(238, 238, 238); font-family: Consolas, Menlo, Monaco, \'Lucida Console\', \'Liberation Mono\', \'DejaVu Sans Mono\', \'Bitstream Vera Sans Mono\', \'Courier New\', monospace, serif; padding: 0px; margin: 0px;"><span style="color:#cc0000;"><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;"><span style="font-family: Arial; font-size: 14px; line-height: 26px;">tvExecutor</span></span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">.</span><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">setTag</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">(</span><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">R</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">.</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;"><span color="#00008b">id.tag_a</span></span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">,</span><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;"> </span><span class="str" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">"逗比"</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">);</span><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">
<span style="font-family: Arial; font-size: 14px; line-height: 26px;">tvExecutor</span></span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">.</span><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">setTag</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">(</span><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">R</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">.</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;"><span color="#00008b">id.tag_b</span></span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">,</span><span class="pln" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;"> </span><span class="str" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">"2货"</span><span class="pun" style="border: 0px; vertical-align: baseline; background-color: transparent; padding: 0px; margin: 0px;">);</span></span></code>

其有用的最多的是convertView中

convertView中的TAG

1.         对于使用了LayoutInflater对象进行View扩充的Tag的使用

         在之前。在adapter中,我们在getView中是这么些的代码:

public View getView(int position, View convertView, ViewGroup parent) {

 

       ViewHolder holder = null;

       if (convertView == null) {

 

          holder = new ViewHolder();

 

          convertView = inflater.inflate(R.layout.vlist2null);

          holder.img = (ImageView) convertView.findViewById(R.id.img);

          holder.title = (TextView) convertView.findViewById(R.id.title);

           holder.info = (TextView)

convertView.findViewById(R.id.info);

          // setTag的妙用

          convertView.setTag(holder);

 

       } else {

 

          holder = (ViewHolder) convertView.getTag();

       }

 

 ……略

}

样例3   在onClick点击事件中。使用tag

 View中的setTag(Onbect)表示给View加入一个格外的数据。以后能够用getTag()将这个数据取出来。

  能够用在多个Button加入一个监听器,每一个Button都设置不同的setTag。这个监听器就通过getTag来分辨是哪个Button 被按下。

  import android.app.Activity;

  import android.os.Bundle;

  import android.view.View;

  import android.widget.Button;

  public class Main extends Activity {

  @Override

  public void onCreate(Bundle savedInstanceState) {

  super.onCreate(savedInstanceState);

  setContentView(R.layout.main);

  Button button1 = (Button) findViewById(R.id.Button01);

  Button button2 = (Button) findViewById(R.id.Button02);

  Button button3 = (Button) findViewById(R.id.Button03);

  Button button4 = (Button) findViewById(R.id.Button04);

  MyListener listener = new MyListener();

  button1.setTag(1);

  button1.setOnClickListener(listener);

  button2.setTag(2);

  button2.setOnClickListener(listener);

  button3.setTag(3);

  button3.setOnClickListener(listener);

  button4.setTag(4);

  button4.setOnClickListener(listener);

  }

  public class MyListener implements View.OnClickListener {

  @Override

  public void onClick(View v) {

  int tag = (Integer) v.getTag();

  switch (tag) {

  case 1:

  System.out.println("button1 click");

  break;

  case 2:

  System.out.println("button2 click");

  break;

  case 3:

  System.out.println("button3 click");

  break;

  case 4:

  System.out.println("button4 click");

  break;

  }

  }

  }

  }




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