如何修复此代码中的弃用警告?或者，还有其他的选择吗?
Handler().postDelayed({
context?.let {
//code
}
}, 3000)
当前回答
Java的答案
我写了一个容易使用的方法。您可以在项目中直接使用此方法。delayTimeMillis可以是2000，这意味着该代码将在2秒后运行。
private void runJobWithDelay(int delayTimeMillis){
new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
@Override
public void run() {
//todo: you can call your method what you want.
}
}, delayTimeMillis);
}
其他回答
如果你想避免在Kotlin (?或者!!)你可以使用loop . getmainlooper()如果你的Handler正在处理一些UI相关的事情，像这样:
Handler(Looper.getMainLooper()).postDelayed({
Toast.makeText(this@MainActivity, "LOOPER", Toast.LENGTH_SHORT).show()
}, 3000)
注意:如果使用fragment，请使用requireContext()而不是this@MainActivity。
从API级别30开始，有2个构造函数已弃用。
处理程序() 处理程序(Handler.Callback)
谷歌解释了以下原因。
Implicitly choosing a Looper during Handler construction can lead to bugs where operations are silently lost (if the Handler is not expecting new tasks and quits), crashes (if a handler is sometimes created on a thread without a Looper active), or race conditions, where the thread a handler is associated with is not what the author anticipated. Instead, use an Executor or specify the Looper explicitly, using Looper#getMainLooper, {link android.view.View#getHandler}, or similar. If the implicit thread local behavior is required for compatibility, use new Handler(Looper.myLooper(), callback) to make it clear to readers.
解决方案1:使用Executor
1. 执行主线程中的代码。
Java
// Create an executor that executes tasks in the main thread.
Executor mainExecutor = ContextCompat.getMainExecutor(this);
// Execute a task in the main thread
mainExecutor.execute(new Runnable() {
@Override
public void run() {
// You code logic goes here.
}
});
科特林
// Create an executor that executes tasks in the main thread.
val mainExecutor = ContextCompat.getMainExecutor(this)
// Execute a task in the main thread
mainExecutor.execute {
// You code logic goes here.
}
2. 在后台线程中执行代码
Java
// Create an executor that executes tasks in a background thread.
ScheduledExecutorService backgroundExecutor = Executors.newSingleThreadScheduledExecutor();
// Execute a task in the background thread.
backgroundExecutor.execute(new Runnable() {
@Override
public void run() {
// Your code logic goes here.
}
});
// Execute a task in the background thread after 3 seconds.
backgroundExecutor.schedule(new Runnable() {
@Override
public void run() {
// Your code logic goes here
}
}, 3, TimeUnit.SECONDS);
科特林
// Create an executor that executes tasks in a background thread.
val backgroundExecutor: ScheduledExecutorService = Executors.newSingleThreadScheduledExecutor()
// Execute a task in the background thread.
backgroundExecutor.execute {
// Your code logic goes here.
}
// Execute a task in the background thread after 3 seconds.
backgroundExecutor.schedule({
// Your code logic goes here
}, 3, TimeUnit.SECONDS)
注意:使用后记得关闭执行程序。
backgroundExecutor.shutdown(); // or backgroundExecutor.shutdownNow();
3.在后台线程中执行代码，在主线程中更新UI。
Java
// Create an executor that executes tasks in the main thread.
Executor mainExecutor = ContextCompat.getMainExecutor(this);
// Create an executor that executes tasks in a background thread.
ScheduledExecutorService backgroundExecutor = Executors.newSingleThreadScheduledExecutor();
// Execute a task in the background thread.
backgroundExecutor.execute(new Runnable() {
@Override
public void run() {
// Your code logic goes here.
// Update UI on the main thread
mainExecutor.execute(new Runnable() {
@Override
public void run() {
// You code logic goes here.
}
});
}
});
科特林
// Create an executor that executes tasks in the main thread.
val mainExecutor: Executor = ContextCompat.getMainExecutor(this)
// Create an executor that executes tasks in a background thread.
val backgroundExecutor = Executors.newSingleThreadScheduledExecutor()
// Execute a task in the background thread.
backgroundExecutor.execute {
// Your code logic goes here.
// Update UI on the main thread
mainExecutor.execute {
// You code logic goes here.
}
}
解决方案2:通过使用以下构造函数之一显式地指定一个Looper。
处理器(是我) 处理器(卢珀指导员回调)。
1. 执行主线程中的代码
1.1. Handler with a Looper
Java
Handler mainHandler = new Handler(Looper.getMainLooper());
科特林
val mainHandler = Handler(Looper.getMainLooper())
1.2带有循环程序和处理程序的处理程序。回调
Java
Handler mainHandler = new Handler(Looper.getMainLooper(), new Handler.Callback() {
@Override
public boolean handleMessage(@NonNull Message message) {
// Your code logic goes here.
return true;
}
});
科特林
val mainHandler = Handler(Looper.getMainLooper(), Handler.Callback {
// Your code logic goes here.
true
})
2. 在后台线程中执行代码
2.1. Handler with a Looper
Java
// Create a background thread that has a Looper
HandlerThread handlerThread = new HandlerThread("HandlerThread");
handlerThread.start();
// Create a handler to execute tasks in the background thread.
Handler backgroundHandler = new Handler(handlerThread.getLooper());
科特林
// Create a background thread that has a Looper
val handlerThread = HandlerThread("HandlerThread")
handlerThread.start()
// Create a handler to execute tasks in the background thread.
val backgroundHandler = Handler(handlerThread.looper)
2.2. Handler with一个Looper和一个Handler。回调
Java
// Create a background thread that has a Looper
HandlerThread handlerThread = new HandlerThread("HandlerThread");
handlerThread.start();
// Create a handler to execute taks in the background thread.
Handler backgroundHandler = new Handler(handlerThread.getLooper(), new Handler.Callback() {
@Override
public boolean handleMessage(@NonNull Message message) {
// Your code logic goes here.
return true;
}
});
科特林
// Create a background thread that has a Looper
val handlerThread = HandlerThread("HandlerThread")
handlerThread.start()
// Create a handler to execute taks in the background thread.
val backgroundHandler = Handler(handlerThread.looper, Handler.Callback {
// Your code logic goes here.
true
})
注意:使用后记得释放线程。
handlerThread.quit(); // or handlerThread.quitSafely();
3.在后台线程中执行代码，在主线程中更新UI。
Java
// Create a handler to execute code in the main thread
Handler mainHandler = new Handler(Looper.getMainLooper());
// Create a background thread that has a Looper
HandlerThread handlerThread = new HandlerThread("HandlerThread");
handlerThread.start();
// Create a handler to execute in the background thread
Handler backgroundHandler = new Handler(handlerThread.getLooper(), new Handler.Callback() {
@Override
public boolean handleMessage(@NonNull Message message) {
// Your code logic goes here.
// Update UI on the main thread.
mainHandler.post(new Runnable() {
@Override
public void run() {
}
});
return true;
}
});
科特林
// Create a handler to execute code in the main thread
val mainHandler = Handler(Looper.getMainLooper())
// Create a background thread that has a Looper
val handlerThread = HandlerThread("HandlerThread")
handlerThread.start()
// Create a handler to execute in the background thread
val backgroundHandler = Handler(handlerThread.looper, Handler.Callback {
// Your code logic goes here.
// Update UI on the main thread.
mainHandler.post {
}
true
})
如果你使用变量作为处理程序和可运行的，然后像这样使用它。
private Handler handler;
private Runnable runnable;
handler = new Handler(Looper.getMainLooper());
handler.postDelayed(runnable = () -> {
// Do delayed stuff here
handler.postDelayed(runnable, 1000);
}, delay);
你还需要删除onDestroy()中的回调
@Override
public void onDestroy() {
super.onDestroy();
if (handler != null) {
handler.removeCallbacks(runnable);
}
}
根据文档(https://developer.android.com/reference/android/os/Handler#Handler()):
Implicitly choosing a Looper during Handler construction can lead to bugs where operations are silently lost (if the Handler is not expecting new tasks and quits), crashes (if a handler is sometimes created on a thread without a Looper active), or race conditions, where the thread a handler is associated with is not what the author anticipated. Instead, use an Executor or specify the Looper explicitly, using Looper#getMainLooper, {link android.view.View#getHandler}, or similar. If the implicit thread local behavior is required for compatibility, use new Handler(Looper.myLooper()) to make it clear to readers.
我们应该停止使用没有Looper的构造函数，而是指定一个Looper。
在Handler构造函数中提供一个循环器
Handler(Looper.getMainLooper())
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