Handler的实质就是异步消息处理。
实例一：
Handler的基本用法
XML布局代码:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/tvResult" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="高兴点，未来不是梦"/> <Button android:id="@+id/btnStart" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="动起来！"/> <Button android:id="@+id/btnEnd" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="歇会吧！"/> <Button android:id="@+id/btnClear" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="清零！"/> </LinearLayout>
Java代码：
public class HandlerActivity extends Activity {
private Button btnStart;
private Button btnEnd;
private Button btnClear;
private TextView tvResult;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initContent();
}
private void initContent() {
setContentView(R.layout.activity_handler);
tvResult = (TextView) findViewById(R.id.tvResult);
btnStart = (Button) findViewById(R.id.btnStart);
btnEnd = (Button) findViewById(R.id.btnEnd);
btnClear = (Button) findViewById(R.id.btnClear);
btnStart.setOnClickListener(new StartButtonListener());
btnEnd.setOnClickListener(new EndButtonListener());
btnClear.setOnClickListener(new ClearButtonListener());
}
// 创建一个Handler对象
Handler handler = new Handler();
private int i = 0;
// 将要执行的操作写在线程对象的run方法当中
Runnable updateThread = new Runnable() {
public void run() {
System.out.println("高兴点，追梦！--" + i);
tvResult.setText("高兴点，追梦！--" + i);
i++;
// 在run方法内部，执行postDelayed或者是post方法
handler.postDelayed(updateThread, 3000);
};
};
class StartButtonListener implements OnClickListener {
@Override
public void onClick(View v) {
// 调用Handler的post方法，将要执行的线程对象添加到队列当中
handler.post(updateThread);
}
}
class EndButtonListener implements OnClickListener {
@Override
public void onClick(View v) {
// 调用Handler的post方法，将要updateThread从队列当中移除
handler.removeCallbacks(updateThread);
}
}
class ClearButtonListener implements OnClickListener {
@Override
public void onClick(View v) {
// 调用Handler的post方法，将要updateThread从队列当中移除
handler.removeCallbacks(updateThread);
i = 0;
tvResult.setText("高兴点，未来不是梦");
}
}
}
实例二：
Handler与ProgressBar的结合使用
XML布局代码:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <ProgressBar android:id="@+id/progressbar" style="?android:attr/progressBarStyleHorizontal" android:layout_width="200dp" android:layout_height="wrap_content" android:visibility="gone" /> <Button android:id="@+id/btnStart" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="前进吧，小摩托！" /> </LinearLayout>
Java代码：
public class HandlerProgressBarActivity extends Activity {
private ProgressBar progressbar;
private Button btnStart;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initContent();
}
private void initContent() {
setContentView(R.layout.activity_handlerprogressbar);
progressbar = (ProgressBar) findViewById(R.id.progressbar);
btnStart = (Button) findViewById(R.id.btnStart);
btnStart.setOnClickListener(new StartOnClick());
}
class StartOnClick implements OnClickListener {
@Override
public void onClick(View v) {
progressbar.setVisibility(View.VISIBLE);
updateBarHandler.post(updateThread);
}
}
Handler updateBarHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
progressbar.setProgress(msg.arg1);
updateBarHandler.post(updateThread);
}
};
Runnable updateThread = new Runnable() {
int i = 0;
@Override
public void run() {
System.out.println("Begin Thread!" + i);
i = i + 10;
Message msg = updateBarHandler.obtainMessage();
msg.arg1 = i;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
updateBarHandler.sendMessage(msg);
if (i == 100) {
updateBarHandler.removeCallbacks(updateThread);
}
}
};
}
实例三：
Handler与线程的关系（一）
XML布局代码:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:text="前进吧，小摩托！" /> </LinearLayout>
Java代码：
public class HandlerThreadActivity extends Activity {
private Handler handler = new Handler();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initContent();
}
private void initContent() {
handler.post(r);
setContentView(R.layout.activity_handlerthread);
System.out.println("activity--->"+Thread.currentThread().getId());
System.out.println("activityname--->"+Thread.currentThread().getName());
}
Runnable r = new Runnable(){
@Override
public void run() {
System.out.println("handler--->"+Thread.currentThread().getId());
System.out.println("handlername--->"+Thread.currentThread().getName());
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
}
实例四：
Handler与线程的关系（二）
XML布局代码:
同【实例三】中的布局代码
Java代码：
public class HandlerThreadActivity extends Activity {
private Handler handler = new Handler();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initContent();
}
private void initContent() {
setContentView(R.layout.activity_handlerthread);
Thread t = new Thread(r);
t.start();
System.out.println("activity--->" + Thread.currentThread().getId());
System.out.println("activityname--->"
+ Thread.currentThread().getName());
}
Runnable r = new Runnable() {
@Override
public void run() {
System.out.println("handler--->" + Thread.currentThread().getId());
System.out.println("handlername--->"
+ Thread.currentThread().getName());
try {
Thread.sleep(10000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
}
实例五：
Handler实现真正的异步消息处理，在新线程中处理消息
XML布局代码:
同【实例三】中的布局代码
Java代码：
public class HandlerMsgActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initContent();
}
private void initContent() {
setContentView(R.layout.activity_handlermsg);
// 打印当前线程
System.out.println("activity---->" + Thread.currentThread().getId());
// 生成一个HandlerThread对象（具有循环处理消息的功能），实现了Looper来处理消息队列
HandlerThread handlerThread = new HandlerThread("handler_thread");
// 让一个线程运行，必须用[线程名称].start()方法
handlerThread.start();
MyHandler myHandler = new MyHandler(handlerThread.getLooper());
Message msg = myHandler.obtainMessage();
// 将msg发动到目标对象，所谓目标对象，就是生成msg的handler对象
msg.sendToTarget();
}
class MyHandler extends Handler {
public MyHandler() {
}
public MyHandler(Looper looper) {
super(looper);
}
@Override
// 每当向Handler发送一个msg的时候，就会执行handleMessage()方法
public void handleMessage(Message msg) {
System.out.println("handler---->" + Thread.currentThread().getId());
System.out.println("handlerMessage");
}
}
}
实例六：
Handler实现真正的异步消息处理，在新线程中处理消息
XML布局代码:
同【实例三】中的布局代码
Java代码：
public class HandlerMsgActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initContent();
}
private void initContent() {
setContentView(R.layout.activity_handlermsg);
// 打印当前线程
System.out.println("activity---->" + Thread.currentThread().getId());
// 生成一个HandlerThread对象（具有循环处理消息的功能），实现了Looper来处理消息队列
HandlerThread handlerThread = new HandlerThread("handler_thread");
// 让一个线程运行，必须用[线程名称].start()方法
handlerThread.start();
MyHandler myHandler = new MyHandler(handlerThread.getLooper());
Message msg = myHandler.obtainMessage();
Bundle b = new Bundle();
b.putInt("age", 20);
b.putString("name", "滔滔1024");
msg.setData(b); //msg.arg1与msg.arg2的消耗比msg.setData()小，但只能传递整型变量
// 将msg发动到目标对象，所谓目标对象，就是生成msg的handler对象，本例中是发送到MyHandler对象中
msg.sendToTarget();
}
class MyHandler extends Handler {
public MyHandler() {
}
public MyHandler(Looper looper) {
super(looper);
}
@Override
// 每当向Handler发送一个msg的时候，就会执行handleMessage()方法
public void handleMessage(Message msg) {
Bundle b = msg.getData();
int age = b.getInt("age");
String name = b.getString("name");
System.out.println("age->"+age+"\nname->"+name);
System.out.println("handler---->" + Thread.currentThread().getId());
System.out.println("handlerMessage");
}
}
}