RK3288 + Android 7.1 + AndroidStudio 4.0.1
使用Handler
Handler.postDelayed(Runnable, Int)
时, Runnable.run中的代码不执行
Handler 部分的代码:
static class H extends Handler{
final static int MSG_REFRESH_TIME = 0;
WeakReference a;
H(KidsLauncher lk){
a = new WeakReference<>(lk);
}
@Override
public void handleMessage(Message msg) {
switch(msg.what){
case MSG_REFRESH_TIME:
a.get().refreshTime();
break;
}
}
/*@Override
public boolean sendMessageAtTime(Message msg, long uptimeMillis) {
Logger.d("sendmessageAtTime " + msg.what + " " + uptimeMillis + ":" + SystemClock.uptimeMillis());
return super.sendMessageAtTime(msg, uptimeMillis);
}*/
}
void refreshTime(){
tvTime.setText(TimeUtils.getTimeString());
h.removeMessages(H.MSG_REFRESH_TIME);
h.sendEmptyMessageDelayed(H.MSG_REFRESH_TIME, 1000);
}
尝试过的解决方案:
查阅相关源码及文章:
Handler sendMessageDelayed()/postDelayed()机制详解
尝试把上面注释代码放开, 输出LOG, 终于发现了问题所在.
原因: 在应用中, 定义一个消息类型为 MSG_REFRESH_TIME=0; 在启动后, 会自循环更新当前的时间.
考虑下这样一个问题: Handler.post后, 最终enqueueMessage时, Message.what是多少? 答案是 0
//frameworks/base/core/java/android/os/Handler.java
public final boolean postDelayed(Runnable r, long delayMillis)
{
return sendMessageDelayed(getPostMessage(r), delayMillis);
}
private static Message getPostMessage(Runnable r) {
Message m = Message.obtain();
m.callback = r;
return m;
}
public final boolean sendMessageDelayed(Message msg, long delayMillis)
{
if (delayMillis < 0) {
delayMillis = 0;
}
return sendMessageAtTime(msg, SystemClock.uptimeMillis() + delayMillis);
}
public boolean sendMessageAtTime(Message msg, long uptimeMillis) {
MessageQueue queue = mQueue;
if (queue == null) {
RuntimeException e = new RuntimeException(
this + " sendMessageAtTime() called with no mQueue");
Log.w("Looper", e.getMessage(), e);
return false;
}
return enqueueMessage(queue, msg, uptimeMillis);
}
不管是new Message(), 还是Message.obtain(), 在初始时, 基本都是0
再看下面这段代码:
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
h = new H(this);
h.postDelayed(new Runnable() {
@Override
public void run() {
Logger.d("run in post Delayed");
}
}, 2000);
h.removeMessages(0);
}
代码中 "run in post Delayed" 这个LOG, 是不会打印出来的, 原因是, Message已经从队列移除了.
同理, 在使用MSG_REFRESH_TIME 更新时间的时, 执行refreshTime后, 队列中, 所有的带Runnable的Message已经被h.removeMessages(H.MSG_REFRESH_TIME); 移出了队列.
所以这个问题是, 自己挖坑, 再把自己埋了...