2011-2-14 | Android Handler

2010-2-14

关键词：Android Handler

如下的代码实现一个Iphone 上的一个通过按backspace键后，数字过多消除的按钮事件。事件的原理如下，事件要的效果是这样的，当长按消除按钮后，数字会慢慢消除，当消除5个字符后继续消除的话消除速度会增快。通过这份代码可以帮助我们较好的初识Handler的工作机制。

 

package com.william.handlertest;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class HandlerTest extends Activity implements Runnable{

     private EditText content = null;
     private Button backspace = null;

     private boolean isStop = false;
     private Handler mHandler = null;

     private class BackspaceOnTouchListener implements Button.OnTouchListener{

        @Override
         public boolean onTouch(View v, MotionEvent event) {
             switch(event.getAction()){
             case MotionEvent.ACTION_DOWN :
                isStop = true;
                mHandler = getHandler(content);
                 new Thread(HandlerTest. this).start();
                 break;
             case MotionEvent.ACTION_UP :
                isStop = false;
                 break;
             default :
                 break;
            }
             return false;
        }

    }

    @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        content = (EditText) findViewById(R.id.content);
        content.setCursorVisible(false);

        backspace = (Button) findViewById(R.id.backspace);
        backspace.setOnTouchListener( new BackspaceOnTouchListener());
    }

     private Handler getHandler( final TextView content){
         return new Handler(){

            @Override
             public void handleMessage(Message msg) {
                content.setText((String)msg.obj);
                 super.handleMessage(msg);
            }

        };
    }

    @Override
     public void run() {
         try{
             int i = 0;

             do{

                i ++;
                Thread.sleep((i > 5 ? 100 : 500));

                String contentStr = this.content.getText().toString();
                 if(contentStr.length() == 0){
                     break;
                }
                contentStr = contentStr.substring( 0, contentStr.length() - 1);

                Message msg = mHandler.obtainMessage();
                msg.obj =contentStr;
                msg.sendToTarget();

            } while(isStop);

        } catch(Exception e){
            e.printStackTrace();
        }
    }

}

 

    代码参考了如下博文，在其消除至无字符时异常退出的非完美代码上进行了修改。

     http://www.cnblogs.com/TerryBlog/archive/2010/08/25/1808445.html

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