Android之Handler详解（二）

来源：互联网发布：人工智能的应用新闻编辑：程序博客网时间：2024/05/21 10:09

二：sendMessage版本的Handler的使用

这里介绍几种模型:

a、默认的Handler（消息处理队列挂在主线程上）

Java代码复制代码收藏代码

[java] view plaincopy

<span style="font-size:16px;"> package com.dxyh.test;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity
implements OnClickListener {
private final static String TAG = "HandlerTest";
private final static int TASK_BEGIN = 1;
private final static int TASK_1 = 2;
private final static int TASK_2 = 3;
private final static int TASK_END = 4;
private Button btnStart = null;
private Button btnStop = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btnStart = (Button) findViewById(R.id.btn_start);
btnStart.setOnClickListener(this);
btnStop = (Button) findViewById(R.id.btn_stop);
btnStop.setOnClickListener(this);
Log.i(TAG, "[M_TID:" + Thread.currentThread().getId() + "]");
}
Handler mHandler = new Handler() {
// 注意：在各个case后面不能做太耗时的操作，否则出现ANR对话框
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case TASK_BEGIN:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_BEGIN");
break;
case TASK_1:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_1");
break;
case TASK_2:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_2");
break;
case TASK_END:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_END");
finish();
break;
}
super.handleMessage(msg);
}
};
public void onClick(View view) {
switch (view.getId()) {
case R.id.btn_start:
// 启动任务（消息只有标识，立即投递）
mHandler.sendEmptyMessage(TASK_BEGIN);
Log.i(TAG, "Send TASK_BEGIN to handler.");
// 开始任务1（在mHandler的消息队列中获取一个Message对象，避免重复构造）
Message msg1 = mHandler.obtainMessage(TASK_1);
msg1.obj = "This is task1";
mHandler.sendMessage(msg1);
Log.i(TAG, "Send TASK_1 to handler.");
// 开启任务2（和上面类似）
Message msg2 = Message.obtain();
msg2.arg1 = 10;
msg2.arg2 = 20;
msg2.what = TASK_2;
mHandler.sendMessage(msg2);
Log.i(TAG, "Send TASK_2 to handler.");
break;
case R.id.btn_stop:
// 结束任务（空消息体，延时2s投递）
mHandler.sendEmptyMessageDelayed(TASK_END, 2000);
Log.i(TAG, "Send TASK_END to handler.");
break;
}
}
} </span>

运行结果：

b、消息队列仍绑定在主线程上，但在子线程中发送消息。

Java代码

[java] view plaincopy

<span style="font-size:16px;"> package com.dxyh.test;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
public class MainActivity extends Activity {
private final static String TAG = "HandlerTest";
private final static int TASK_BEGIN = 1;
private final static int TASK_1 = 2;
private final static int TASK_2 = 3;
private final static int TASK_END = 4;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Log.i(TAG, "[M_TID:" + Thread.currentThread().getId() + "]" +
"This is in main thread.");
workThread.start();
}
Handler mHandler = new Handler() {
// 注意：在各个case后面不能做太耗时的操作，否则出现ANR对话框
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case TASK_BEGIN:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_BEGIN");
break;
case TASK_1:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_1");
break;
case TASK_2:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_2");
break;
case TASK_END:
Log.i(TAG, "[H_TID:" +
Thread.currentThread().getId() + "] Get TASK_END");
finish();
break;
}
super.handleMessage(msg);
}
};
Thread workThread = new Thread() {
// 你可以在run方法内做任何耗时的操作，然后将结果以消息形式投递到主线程的消息队列中
@Override
public void run() {
// 启动任务（消息只有标识，立即投递）
mHandler.sendEmptyMessage(TASK_BEGIN);
Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" +
"Send TASK_START to handler.");
// 开始任务1（在mHandler的消息队列中获取一个Message对象，避免重复构造）
Message msg1 = mHandler.obtainMessage(TASK_1);
msg1.obj = "This is task1";
mHandler.sendMessage(msg1);
Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" +
"Send TASK_1 to handler.");
// 开启任务2（和上面类似）
Message msg2 = Message.obtain();
msg2.arg1 = 10;
msg2.arg2 = 20;
msg2.what = TASK_2;
mHandler.sendMessage(msg2);
Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" +
"Send TASK_2 to handler.");
// 结束任务（空消息体，延时2s投递）
mHandler.sendEmptyMessageDelayed(TASK_END, 2000);
Log.i(TAG, "[S_TID:" + Thread.currentThread().getId() + "]" +
"Send TASK_END to handler.");
}
};
}
</span>

运行结果：