Handler主要用于接受子线程发送的数据, 并用此数据配合主线程更新UI,因为更新UI只能在主线程中进行。
Handler作为线程通讯工具类。用于传递消息。它有两个队列:
下例给出两个个简单用法:
public class MainActivity extends Activity { private TextView mTextView; private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { // 接收消息并且去更新UI线程上的控件内容 if (msg.what == 0) { mTextView.setText(String.valueOf(msg.obj)); } super.handleMessage(msg); } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mTextView = (TextView) findViewById(R.id.text); new Thread() { @Override public void run() { try { for (int i = 0; i < 100; i++) { Thread.sleep(500); Message msg = new Message(); msg.what = 0; msg.obj = "更新后的值:" + i; handler.sendMessage(msg);//向主线程的handler发消息 } } catch (InterruptedException e) { e.printStackTrace(); } } }.start(); } }
public class MainActivity extends Activity { private static final String TAG_ACTIVITY = "MainActivity"; private static int tick = 0; private TextView mTextView; private Button mbutton; private Handler handler = new Handler() { @Override public void handleMessage(Message msg) { // 接收消息并且去更新UI线程上的控件内容 super.handleMessage(msg); if (msg.arg1 == 0) { mTextView.setText(String.valueOf(msg.obj)); } //重新把线程加入线程队列,延迟1000ms handler.postDelayed(updateThread,1000); } }; Runnable updateThread = new Runnable(){ @Override public void run() { Message msg = handler.obtainMessage(); msg.arg1 = 0; msg.obj = "更新后的值" + tick++; if(10 == tick){ //移除该线程 handler.removeCallbacks(updateThread); return; } handler.sendMessage(msg);//向主线程的handler发消息 Log.i(TAG_ACTIVITY, String.valueOf(msg.obj)); } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mTextView = (TextView) findViewById(R.id.text); mbutton = (Button) findViewById(R.id.button1); mbutton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { //把线程加入线程队列 handler.post(updateThread); } }); } }
原文:http://www.cnblogs.com/Fredric-2013/p/4253911.html