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Android 中的观察者模式

发布于 2024-09-14 03:49:51 字数 330 浏览 3 评论 0原文

我有一个问题。
1.我有两个线程：“worker”和“UI”线程。
2. Worker持续等待服务器端的数据，获取到后通知UI线程。
3. 更新 UI 时，屏幕上会显示 Toast 消息。

第 3 步有问题，如下所示：

android.view.ViewRoot$CalledFromWrongThreadException：仅创建视图层次结构的原始线程可以触摸其视图。

使用 mHandler，runOnUIThread 会减慢 UI 线程（UI 显示 webview），因为我必须不断检查来自服务器的数据。

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初见终念 2024-09-21 03:49:51

使用 AsyncTask 来实现这一点。重写 doInBackground 来获取数据（它在单独的线程上执行），然后重写 onPostExecute() 以显示 toast（它在 UI 线程上执行）。

这是一个很好的例子 http://www.screaming-penguin.com/node/7746

这里是官方文档。

UPD：有关如何处理部分进度的示例。

    class ExampleTask extends AsyncTask<String, String, String>{

    @Override
    protected String doInBackground(String... params) {
        while(true){
            //Some logic on data recieve..
            this.publishProgress("Some progress");
            //seee if need to stop the thread.
            boolean stop = true;
            if(stop){
                break;
            }
        }
        return "Result";
    }

    @Override
    protected void onProgressUpdate(String... values) {
        super.onProgressUpdate(values);
        //UI tasks on particular progress...
    }
}

Use AsyncTask to implement this. Override doInBackground to get the data (it is executed on the separate thread), then override onPostExecute() to show the toast (it is executed on the UI thread).

Here is good example http://www.screaming-penguin.com/node/7746

And here is official docs.

UPD: Example on how to handle partial progress.

    class ExampleTask extends AsyncTask<String, String, String>{

    @Override
    protected String doInBackground(String... params) {
        while(true){
            //Some logic on data recieve..
            this.publishProgress("Some progress");
            //seee if need to stop the thread.
            boolean stop = true;
            if(stop){
                break;
            }
        }
        return "Result";
    }

    @Override
    protected void onProgressUpdate(String... values) {
        super.onProgressUpdate(values);
        //UI tasks on particular progress...
    }
}

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靖瑶 2024-09-21 03:49:51

我会使用一项服务，并将您的活动绑定到该服务。然后服务可以在有新数据时发送广播

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⊕婉儿 2024-09-21 03:49:51

Android 中的对象观察者模式？

定义： 观察者模式定义了对象之间的一对多依赖关系，以便当一个对象更改状态时，它的所有依赖项都会收到通知，并且自动更新。

       The objects which are watching the state changes are called observer. Alternatively observer are also called listener. The object which is being watched is called subject.

Example: View A is the subject. View A displays the temperature of a     container.  View B display a green light is the temperature is above 20 degree Celsius. Therefore View B registers itself as a Listener to View A.  If the temperature of View A is changed an event is triggered. That is event is send to all registered listeners in this example View B. View B receives the changed data and can adjust his display.

 Evaluation:  The subject can registered an unlimited number of observers. If a new listener should register at the subject no code change in the subject is necessary.

Object Observer pattern in Android ?

Definition: The Observer Pattern defines a one-to-many dependency between objects so that when one object changes state, all of its dependents are notified and updated automatically.

       The objects which are watching the state changes are called observer. Alternatively observer are also called listener. The object which is being watched is called subject.

Example: View A is the subject. View A displays the temperature of a     container.  View B display a green light is the temperature is above 20 degree Celsius. Therefore View B registers itself as a Listener to View A.  If the temperature of View A is changed an event is triggered. That is event is send to all registered listeners in this example View B. View B receives the changed data and can adjust his display.

 Evaluation:  The subject can registered an unlimited number of observers. If a new listener should register at the subject no code change in the subject is necessary.

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