Android开发中，使用线程应该注意的问题!

原帖地址：http://blog.csdn.net/Android_Tutor/archive/2010/08/24/5834246.aspx

我们都知道Hanlder是线程与Activity通信的桥梁，我们在开发好多应用中会用到线程，有些人处理不当，会导致当程序结束时，线程并没有被销毁，而是一直在后台运行着，当我们重新启动应用时，又会重新启动一个线程，周而复始，你启动应用次数越多，开启的线程数就越多，你的机器就会变得越慢。

为了方便 大家理解，我写一个简单的Demo.功能就是每2秒中将应用的Title更换一次。具体步骤如下:

第一步:新建一个Android工程命名为ThreadDemo。

第二步:修改ThreadDemo.java,代码如下:

[c-sharp]
view plaincopyprint?

package com.tutor.thread;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
public class ThreadDemo extends Activity {

private static final String TAG =
"ThreadDemo";
private int count = 0;

private Handler mHandler =
new Handler();

private Runnable mRunnable =
new Runnable() {

public void run() {

//为了方便 查看，我们用Log打印出来

Log.e(TAG, Thread.currentThread().getName() +
" " +count);
count++;
setTitle("" +count);

//每2秒执行一次
mHandler.postDelayed(mRunnable, 2000);

}

};
@Override
public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//通过Handler启动线程

mHandler.post(mRunnable);
}

}

[c-sharp]
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@Override
protected void onDestroy() {

mHandler.removeCallbacks(mRunnable);
super.onDestroy();
}

@Override
protected void onDestroy() {
mHandler.removeCallbacks(mRunnable);
super.onDestroy();
}

所以ThreadDemo.java的完整代码如下:

[c-sharp]
view plaincopyprint?

package com.tutor.thread;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
public class ThreadDemo extends Activity {

private static final String TAG =
"ThreadDemo";
private int count = 0;

private Handler mHandler =
new Handler();

private Runnable mRunnable =
new Runnable() {

public void run() {

//为了方便 查看，我们用Log打印出来

Log.e(TAG, Thread.currentThread().getName() +
" " +count);
count++;
setTitle("" +count);

//每2秒执行一次
mHandler.postDelayed(mRunnable, 2000);

}

};
@Override
public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.main);
//通过Handler启动线程

mHandler.post(mRunnable);
}

@Override
protected void onDestroy() {

//将线程销毁掉

mHandler.removeCallbacks(mRunnable);
super.onDestroy();
}
}