Handler和HandlerThread配合使用¶
参考Android Camera2Basic Sample的handler使用方法
/**
* An additional thread for running tasks that shouldn't block the UI.
*/
private HandlerThread mBackgroundThread;
/**
* A {@link Handler} for running tasks in the background.
*/
private Handler mBackgroundHandler;
/**
* Starts a background thread and its {@link Handler}.
*/
private void startBackgroundThread() {
mBackgroundThread = new HandlerThread("CameraBackground");
mBackgroundThread.start(); // 必须调用start方法
mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
}
/**
* Stops the background thread and its {@link Handler}.
*/
private void stopBackgroundThread() {
mBackgroundThread.quitSafely();
try {
mBackgroundThread.join();
mBackgroundThread = null;
mBackgroundHandler = null;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
使用HandlerThread，可以直接和Handler关联起来，不用再定义线程和Looper。
HandlerThread 源码解析¶
HandlerThread源码如下（Android-27 删除了官方的注释）
package android.os;
import android.annotation.NonNull;
import android.annotation.Nullable;
/**
* 使用前必须调用start()方法
*/
public class HandlerThread extends Thread {
int mPriority;
int mTid = -1;
Looper mLooper;
private @Nullable Handler mHandler;
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;
}
@NonNull
public Handler getThreadHandler() {
if (mHandler == null) {
mHandler = new Handler(getLooper());
}
return mHandler;
}
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;
}
}
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