Android学习笔记——Handler实例
Handler的实质就是异步消息处理。
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实例一:
Handler的基本用法
XML布局代码:
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:
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:
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"); } } }
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