从 API 级别 30 开始，有 2 个构造函数被弃用。
Google 解释了以下原因。
隐式选择 Looper
处理程序构造可能导致操作静默的错误
丢失（如果处理程序不期待新任务并退出），崩溃
（如果有时在没有 Looper 的线程上创建处理程序
活动）或竞争条件，其中与处理程序关联的线程
与作者的预期不同。相反，使用 Executor 或
明确指定 Looper，使用 Looper#getMainLooper, {link
android.view.View#getHandler}，或类似的。如果隐式线程
本地行为是兼容性所必需的，请使用新的
Handler(Looper.myLooper(), callback) 让读者一目了然。
解决方案 1： 使用 Executor
1.在主线程中执行代码。
// 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.
}
});
2.在后台线程中执行代码
// 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 1 second.
backgroundExecutor.schedule(new Runnable() {
@Override
public void run() {
// Your code logic goes here
}
}, 1, TimeUnit.SECONDS);
注意：使用后记得关闭执行器。
backgroundExecutor.shutdown(); // or backgroundExecutor.shutdownNow();
3.在后台线程中执行代码并在主线程中更新UI。
// 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.
}
});
}
});
解决方案 2： 使用以下构造函数之一显式指定 Looper。
1.在主线程中执行代码
1.1. 带有 Looper 的处理程序
Handler mainHandler = new Handler(Looper.getMainLooper());
1.2 带有 Looper 和 Handler.Callback 的处理程序
Handler mainHandler = new Handler(Looper.getMainLooper(), new Handler.Callback() {
@Override
public boolean handleMessage(@NonNull Message message) {
// Your code logic goes here.
return true;
}
});
2.在后台线程中执行代码
2.1. 带有 Looper 的处理程序
// 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());
2.2. 带有 Looper 和 Handler.Callback 的处理程序
// 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;
}
});
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并在主线程中更新UI。
// 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;
}
});