无法在未调用Looper.prepare()的线程内创建处理程序

Question

我有一个活动,并且我有一个班级.

text=new Dynamictext(...);
text.setText("txt");

在我的DynamicText java中,我有这样的代码:

public void setText(String text) {
    this.text=text;
    new asyncCreateText().execute();
    //this.createText(text);
}

//private Handler handler = new Handler();

private class asyncCreateText extends AsyncTask<Void, Void, Void> 
{
    @Override
    protected Void doInBackground(Void... unused) {
        return null;
    }

    @Override
    protected void onPostExecute(Void unused) {

    }
}

我明白了:

ERROR/AndroidRuntime(5176):引起:java.lang.RuntimeException:无法在未调用Looper.prepare()的线程内创建处理程序

我该如何处理这个错误？

ERROR/AndroidRuntime(5370): java.lang.ExceptionInInitializerError
ERROR/AndroidRuntime(5370):     at com.l.start.DynamicText.setText(DynamicText.java:125)
ERROR/AndroidRuntime(5370):     at com.l.start.OpenGLRenderer.initfonts(OpenGLRenderer.java:168)
ERROR/AndroidRuntime(5370):     at com.l.start.OpenGLRenderer.init(OpenGLRenderer.java:119)
ERROR/AndroidRuntime(5370):     at com.l.start.OpenGLRenderer.onSurfaceChanged(OpenGLRenderer.java:90)
ERROR/AndroidRuntime(5370):     at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1120)
ERROR/AndroidRuntime(5370):     at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:975)

ERROR/AndroidRuntime(5370): Caused by: java.lang.RuntimeException: 
    Can't create handler inside thread that has not called Looper.prepare()
ERROR/AndroidRuntime(5370):     at android.os.Handler.<init>(Handler.java:121)
ERROR/AndroidRuntime(5370):     at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421)
ERROR/AndroidRuntime(5370):     at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421)
ERROR/AndroidRuntime(5370):     at android.os.AsyncTask.<clinit>(AsyncTask.java:152)
ERROR/AndroidRuntime(5370):     ... 6 more

Answer 1

错误是不言自明的... doInBackground()在后台线程上运行,因为它不打算循环,所以没有连接到a Looper.

您很可能根本不想直接实例化Handler ...您的doInBackground()实现返回的任何数据都将传递给onPostExecute()在UI线程上运行的数据.

   mActivity = ThisActivity.this; 

    mActivity.runOnUiThread(new Runnable() {
     public void run() {
     new asyncCreateText().execute();
     }
   });

在问题出现后出现的问题:

看起来你正试图AsyncTask从GL渲染线程开始......不要那样做,他们也不会Looper.loop().AsyncTasks实际上只能从UI线程运行.

破坏性最小的解决方案可能是打电话Activity.runOnUiThread()给Runnable你AsyncTask.

Answer 2

以上所有答案都是正确的,但我认为这是最简单的例子:

public class ExampleActivity extends Activity {
    private Handler handler;
    private ProgressBar progress;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        progress = (ProgressBar) findViewById(R.id.progressBar1);
        handler = new Handler();
    }

    public void clickAButton(View view) {
        // Do something that takes a while
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                handler.post(new Runnable() { // This thread runs in the UI
                    @Override
                    public void run() {
                        progress.setProgress("anything"); // Update the UI
                    }
                });
            }
        };
        new Thread(runnable).start();
    }
}

这样做是从一个完全不同的线程更新UI线程中的进度条,该线程通过活动中声明的处理程序的post()方法传递.

希望能帮助到你!

Answer 3

您以这种方式在后台线程中创建处理程序

private void createHandler() {
        Thread thread = new Thread() {
          public void run() {
               Looper.prepare();

               final Handler handler = new Handler();
               handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                       // Do Work
                        handler.removeCallbacks(this);
                        Looper.myLooper().quit();
                   }
                }, 2000);

                Looper.loop();
            }
        };
        thread.start();
    }

Answer 4

Activity.runOnUiThread()不适合我.我通过这种方式创建一个常规线程来解决这个问题:

public class PullTasksThread extends Thread {
   public void run () {
      Log.d(Prefs.TAG, "Thread run...");
   }
}

并以这种方式从GL更新中调用它:

new PullTasksThread().start();

Answer 5

尝试从 UI 线程运行您的 asyntask。当我不这样做时，我遇到了这个问题！