HandlerThread是一种具有消息循环的线程。HandlerThread可以接收消息并处理消息，并执行一些耗时操作，这样UI线程就可以把一些耗时的操作命令发送给HandlerThread，由该线程处理后再发送到主线程返回。这样主线程用于分发和显示，而子线程用于逻辑处理和运算。
HandlerThread使用的样例：
package com.fxb.handlerthead; import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.TextView; public class MainActivity extends Activity implements View.OnClickListener{ private static final String TAG = "HandlerThreadTest";
private static final int WHAT_CALUCULATE = 0x1001;
private static final int WHAT_RESULT = 0x1002; private TextView tvShow;
private Button btnStart;
private HandlerThread handlerThread;
private Handler mainHandler, subHandler;
private int count; @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView(); mainHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
}
};
initThread();
} private void initView(){
tvShow = (TextView)findViewById(R.id.tvShow);
btnStart = (Button)findViewById(R.id.btnStart); btnStart.setOnClickListener(this);
} private void initThread(){
handlerThread = new HandlerThread("myHandlerThread");
handlerThread.start(); subHandler = new Handler(handlerThread.getLooper()){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if(msg.what == WHAT_CALUCULATE){
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
} final int num1 = msg.arg1;
final int num2 = msg.arg2;
final int result = num1 + num2;
mainHandler.post(new Runnable() {
@Override
public void run() {
tvShow.setText(num1+" + "+num2+" = "+result);
}
});
}
}
};
} @Override
public void onClick(View v) {
if(v == btnStart){
mainHandler.postDelayed(new Runnable() {
@Override
public void run() {
count++;
Message msg = subHandler.obtainMessage(WHAT_CALUCULATE, count, count + 1);
msg.sendToTarget(); mainHandler.postDelayed(this, 1000);
}
}, 1000);
}
}
}
当点击Start按钮后，延时500ms后会在tvShow上显示1 + 2 = 3，1s后显示2 + 3 = 5，依次递增。
HandlerThread源码
import android.os.Looper;
public class HandlerThread extends Thread {
int mPriority;
int mTid = -1;
Looper mLooper;
public HandlerThread(String name) {
super(name);
mPriority = Process.THREAD_PRIORITY_DEFAULT;
}
public HandlerThread(String name, int priority) {
super(name);
mPriority = priority;
}
protected void onLooperPrepared() {
}
@Override
public void run() {
mTid = Process.myTid();
Looper.prepare();
synchronized (this) {
mLooper = Looper.myLooper();
notifyAll();
}
Process.setThreadPriority(mPriority);
onLooperPrepared();
Looper.loop();
mTid = -1;
}
public Looper getLooper() {
if (!isAlive()) {
return null;
}
// If the thread has been started, wait until the looper has been created.
synchronized (this) {
while (isAlive() && mLooper == null) {
try {
wait();
} catch (InterruptedException e) {
}
}
}
return mLooper;
}
public boolean quit() {
Looper looper = getLooper();
if (looper != null) {
looper.quit();
return true;
}
return false;
}
public boolean quitSafely() {
Looper looper = getLooper();
if (looper != null) {
looper.quitSafely();
return true;
}
return false;
}
public int getThreadId() {
return mTid;
}
}
getLooper()时，如果没有创建好，则会阻塞，创建好后会唤醒，然后返回。