Android 线程更新UI报错 : Can't create handler inside thread that has not called Looper.prepare()

浏览数：35 / 时间：2015年06月11日

MainActivity中有一个按钮，绑定了save方法

public void save(View view) {
        String title = titleText.getText().toString();
        String timelength = lengthText.getText().toString();

        ExecutorService exec = Executors.newCachedThreadPool();
        exec.execute(new NewsService(getApplicationContext(),title,timelength));
    }

NewsService代码：

@Override
    public void run() {
        String path = "http://192.168.0.102:8080/videonews/ManageServlet";
        Map<String,String> params = new HashMap<String,String>();
        params.put("title",title);
        params.put("timelength",timelength);
        boolean result=false;
        try {
            result = sendGETRequest(path,params);
        } catch (Exception e) {
            e.printStackTrace();
        }

        if(result) {
            Toast.makeText(context, R.string.success, Toast.LENGTH_LONG).show();
        } else {
            Toast.makeText(context,R.string.error,Toast.LENGTH_LONG).show();
        }
    }

报错：

04-18 13:06:36.191    2284-2305/test.example.com.newsmanage E/AndroidRuntime﹕ FATAL EXCEPTION: pool-1-thread-1
    Process: test.example.com.newsmanage, PID: 2284
    java.lang.RuntimeException: Can‘t create handler inside thread that has not called Looper.prepare()
            at android.os.Handler.<init>(Handler.java:200)
            at android.os.Handler.<init>(Handler.java:114)
            at android.widget.Toast$TN.<init>(Toast.java:336)
            at android.widget.Toast.<init>(Toast.java:100)
            at android.widget.Toast.makeText(Toast.java:250)
            at android.widget.Toast.makeText(Toast.java:277)
            at test.example.com.service.NewsService.run(NewsService.java:86)
            at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
            at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
            at java.lang.Thread.run(Thread.java:818)

查了资料，说是Android中不能在子线程中来刷新UI。如果要实现你这功能的话。建议是在你的子线程中添加hander来发送消息更新线程。

下面这样做就OK了

1.在Activity中增加如下代码

private Handler myHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case 0x00 :
                    Toast.makeText(getApplicationContext(),"save success",Toast.LENGTH_SHORT).show();
                    break;
                default:
                    Toast.makeText(getApplicationContext(),"save fail",Toast.LENGTH_SHORT).show();
            }

        }
    };

2.启动线程时，将handler传入:

exec.execute(new NewsService(getApplicationContext(),myHandler,title,timelength));

3.在线程中，发送消息给handler:

@Override
    public void run() {
        String path = "http://192.168.0.102:8080/videonews/ManageServlet";
        Map<String,String> params = new HashMap<String,String>();
        params.put("title",title);
        params.put("timelength",timelength);
        boolean result=false;
        try {
            result = sendGETRequest(path,params);
        } catch (Exception e) {
            e.printStackTrace();
        }
        Message msg = new Message();
        if(result)
            msg.what = 0x00;
        else
            msg.what = 0x01;
        handler.sendMessage(msg);
    }