在 AsyncTask 中添加视图（文本视图）

Question

我使用下面的代码在异步任务中添加文本视图，但是：

07-26 11:40:39.302: E/AndroidRuntime(26715): Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception
07-26 11:40:39.312: E/AndroidRuntime(26715): java.lang.RuntimeException: An error occured while executing doInBackground()
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.os.AsyncTask$3.done(AsyncTask.java:200)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.lang.Thread.run(Thread.java:1096)
07-26 11:40:39.312: E/AndroidRuntime(26715): Caused by: android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.view.ViewRoot.checkThread(ViewRoot.java:2683)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.view.ViewRoot.invalidateChild(ViewRoot.java:570)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.view.ViewRoot.invalidateChildInParent(ViewRoot.java:596)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.view.ViewGroup.invalidateChild(ViewGroup.java:2481)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.view.View.invalidate(View.java:5027)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.view.ViewGroup.addView(ViewGroup.java:1840)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.view.ViewGroup.addView(ViewGroup.java:1821)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at com.learning.chiazi.MainActivity.addTextView(MainActivity.java:180)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at com.learning.chiazi.MainActivity$Proccess.doInBackground(MainActivity.java:243)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at com.learning.chiazi.MainActivity$Proccess.doInBackground(MainActivity.java:1)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at android.os.AsyncTask$2.call(AsyncTask.java:185)
07-26 11:40:39.312: E/AndroidRuntime(26715):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
07-26 11:40:39.312: E/AndroidRuntime(26715):    ... 4 more
07-26 11:40:39.342: E/SemcCheckin(26715): Get crash dump level : java.io.FileNotFoundException: /data/semc-checkin/crashdump

我该如何解决这个问题？

代码：

   public void addTextView(int belowId, int id,String text){
        RelativeLayout rSub= (RelativeLayout) findViewById(R.id.rSub);
        RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.WRAP_CONTENT,
                RelativeLayout.LayoutParams.WRAP_CONTENT);
        lp.addRule(RelativeLayout.BELOW, belowId);
        lp.addRule(RelativeLayout.ALIGN_PARENT_LEFT);

        TextView tv = new TextView(this);
        tv.setId(id);

        tv.setText(text+"\n");
        rSub.addView(tv, lp);

    }

   class Proccess extends AsyncTask<Void, Void, Void>{

        @Override
        protected Void doInBackground(Void... arg0) {
            addTextView(R.id.tvResult, 1234, "s");
            return null;
        }
    }

Answer 1

使用此代码，它对我有用：

public class MainActivity extends Activity {

    Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            // TODO Auto-generated method stub
            super.handleMessage(msg);
            TextView tvMain = (TextView) findViewById(R.id.tvMain);

                tvMain.setText(msg.getData().get("KEY")+"Button Proceed");
            }
        };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        /*Button btnDemo = (Button) findViewById(R.id.btnDemo);
        btnDemo.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                myAsyncTak();
            }


        });*/

        new AddTask().execute();
    }

    private void myAsyncTak() {
        // TODO Auto-generated method stub
        Runnable runnable = new Runnable() {

            @Override
            public void run() {
                // TODO Auto-generated method stub

                TextView textView=new TextView(MainActivity.this);
                textView.setLayoutParams(new RelativeLayout.LayoutParams(LayoutParams.MATCH_PARENT, 50));
                textView.setText("Newly Added TextView");
                View v=View.inflate(MainActivity.this, R.layout.activity_main, null);
                ((RelativeLayout)v).addView(textView);
                setContentView(v);

                Message msg=new Message();
                Bundle bundle=new Bundle();
                bundle.putString("KEY", "Saurabh");
                msg.setData(bundle);
                handler.sendMessage(msg);
                //handler.sendEmptyMessage(0);
            }
        };

        Thread myThread=new Thread(runnable);
        myThread.start();
    }
    public class AddTask extends AsyncTask<String, Integer, String>{

        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
        }

        @Override
        protected String doInBackground(String... params) {
            // TODO Auto-generated method stub
            myAsyncTak();
            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
        }
    }


}

还有这个布局：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" 
    android:id="@+id/rlMain" >

    <TextView android:id="@+id/tvMain"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/btnDemo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tvMain"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="42dp"
        android:text="Demo" />

</RelativeLayout>

Answer 2

像这样在后台运行 UI 线程

@Override
        protected Void doInBackground(Void... arg0) {
            this.runOnUiThread(new Runnable() {
            public void run() {
                addTextView(R.id.tvResult, 1234, "s");
        });
            return null;
        }

Answer 3

UI 作品应位于主线程中。

在 android AsyncTask.doInBackground() 中，顾名思义，仅适用于网络、数据库访问等后台作业。

您的方法addTextView() 应该位于AsyncTask.onPostExecute()

Answer 4

您无法更改doInBackground() 中的 GUI 试试这个，这样您就可以在 UI 线程上进行更改，同时仍然保留 doInBackground() 中的代码：

@Override
    protected Void doInBackground(Void... arg0) {
       Runnable run = new Runnable() 
       {
            public void run() 
            {
                addTextView(R.id.tvResult, 1234, "s");
            }
    }; return null;
}

但请注意，涉及 GUI 更改的操作最好位于 onPostExecute() 或 onCreate() 中。无论如何，这是最佳做法:)

可能需要时间才能完成的操作，例如运行长时间的数据库查询或其他可能强制关闭应用程序的情况，应位于doInBackground()

Answer 5

不能在AsyncTask的doInBackground()方法中添加TextView，因为该方法在backgronud线程中操作，不能在UI Thread中进行操作，尝试将TextView添加到onPreExecute()/onPostExecute() 或出doInBackground()