android - 在旋转之前放置网络调用时如何更新 UI 线程？

Question

好吧，这让我抓狂。我有一个工作线程(网络调用)需要独立于 UI 线程运行(它实际上是一个 ThreadPoolExecutor 但我简化了它以证明我的观点)。如果您以纵向方式运行此代码，没有旋转，文本会更新。我在那里延迟，以便轮换显示我的问题。如果您以纵向开始，并且在文本更新旋转为横向之前，文本不会更新。如果您注释代码，您可以看到监听器触发但文本永远不会更新。

我正在尝试模拟在单独的线程中运行的自定义网络调用，如果用户在两者之间旋转，则可能需要一些时间才能返回，然后数据丢失。我们正试图阻止多个网络调用以节省手机上的数据使用量。

package com.example.test;

import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.content.res.Configuration;
import android.view.Menu;
import android.widget.TextView;
public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    int orientation = getResources().getConfiguration().orientation; 
    if (Configuration.ORIENTATION_LANDSCAPE == orientation) { 
        //Do SomeThing; // Landscape
    } else { 
        startBackgroundWork();
        //Do SomeThing;  // Portrait
    } 

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

private Handler mHandler = new Handler();

public void startBackgroundWork() {
    new WorkingThread(new SomeListener() {
        public void onSomethingDone(final Object result) {

            mHandler.post(new Runnable() {
                public void run() { 
                    ((TextView)findViewById(R.id.text)).setText((String)result);
                    //showMyDialog(result); 
                }
            });

        }    
    }).start();
}

public interface SomeListener {
    public void onSomethingDone(Object result);
}

public class WorkingThread extends Thread {
    private SomeListener mListener;

    public WorkingThread(SomeListener listener) {
        mListener = listener;
    }

    public void run() {
        /* do some work */
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        mListener.onSomethingDone("New Text");
    }
}
}

Answer 1

这是因为在轮换时， Activity 被重新创建，因此您的所有代码都绑定(bind)到旧 Activity 。您应该引用您的工作线程:

private static WorkingThread mWorkingThread;
public void startBackgroundWork() {
    mWorkingThread = new WorkingThread(new SomeListener() {
        public void onSomethingDone(final Object result) {

            mHandler.post(new Runnable() {
                public void run() { 
                    ((TextView)findViewById(R.id.text)).setText((String)result);
                    //showMyDialog(result); 
                }
            });

        }    
    }).start();
}

然后 onCreate 更新它:

public class WorkingThread extends Thread {
    private SomeListener mListener;

    public WorkingThread(SomeListener listener) {
        mListener = listener;
    }

    public void run() {
        /* do some work */
        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        mListener.onSomethingDone("New Text");
    }

    public void updateListener(SomeListener listener) {
        mListener = listener;
    }
}


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    startBackgroundWork();
}

public void startBackgroundWork() {
    if (mWorkingThread == null || mWorkingThread.isFinished()) { // Use a boolean to know if it still running


    mWorkingThread  = new WorkingThread(new SomeListener() {
        public void onSomethingDone(final Object result) {

            mHandler.post(new Runnable() {
                public void run() { 
                    ((TextView)findViewById(R.id.text)).setText((String)result);
                    //showMyDialog(result); 
                }
            });

        }    
    });
        mWorkingThread.start();

    } else { 
        mWorkingThread.updateListener(new SomeListener() {
        public void onSomethingDone(final Object result) {

            mHandler.post(new Runnable() {
                public void run() { 
                    ((TextView)findViewById(R.id.text)).setText((String)result);
                    //showMyDialog(result); 
                }
            });

        }    
    });
    } 
}

但是您可以进行一些改进:

• WorkingThread 类应该是静态的，以避免直接引用旧 Activity :Java: Static vs non static inner class

• 然后引用当前 Activity ，并在重新创建时更新它

• 创建一个更新文本的方法，而不是直接在监听器中编写代码