屏幕上不显示进度对话框 [英] Progress Dialog not show on screen

问题描述

我根据亲爱的Mayank'answer编辑了我的代码，但是在方法开始之前，它没有显示在displayMsg()方法中作为输入发送的任何消息.我应该说MethodTest()是由nfc和onNewIntent(Intent方法)启动的意向)

I edited my code according dear Mayank'answer but It does not show any message that is sended as input in displayMsg() method before method begines..I should say MethodTest() is started with nfc and in method onNewIntent(Intent intent)

@Override
protected void onNewIntent(Intent intent) {
   MethodTest();
    ..............

}

public void MethodTest() {
    DisplayMsg("method 1 is running");
    Method1();

    DisplayMsg("method 2 is running");
    Method2();

    DisplayMsg("method 3 is running");
    Method3();

}

private int DisplayMsg(String msg) {
    totalMsg += msg;
    DisplayMsgClass dc = new DisplayMsgClass();
    dc.doInBackground(totalMsg);
}

private class DisplayMsgClass extends AsyncTask<String, Integer, String> {

    @Override
    protected void onPreExecute() {
         textView.setText("Hello !!!");
        progressBar = (ProgressBar) findViewById(R.id.progressBar1);
        progressBar.setVisibility(View.VISIBLE);
        super.onPreExecute();
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);

    }

    @Override
    protected String doInBackground(String... Messages) {


        return Messages[0];
    }

    @Override
    protected void onPostExecute(String result) {
        progressBar.setVisibility(View.INVISIBLE);

        textView.setText(result);
    }
}

在我的布局中:

<LinearLayout>
<ProgressBar
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:visibility="gone"
    android:id="@+id/progressBar1"
    />
 <TextView
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:id="@+id/textv1"
  android:hint="AppletPass"
  android:gravity="center"/>
 </LinearLayout>

推荐答案

请记住，理想情况下，AsyncTasks应该用于短操作(最多几秒钟).

Remember that AsyncTasks should ideally be used for short operations (a few seconds at the most.)

尝试了解有关AsyncTask的更多信息，并且您的代码中有很多错误

Try to learn more about AsyncTask and there are so many mistakes in your code

1. 请勿手动调用doInBackground().

dc.doInBackground(totalMsg);//错误

DisplayMsg()调用多次，每次创建类DisplayMsgClass的新实例

DisplayMsg() called several times, each time a new instance of class DisplayMsgClass created

DisplayMsgClass dc = new DisplayMsgClass();//错误

onPreExecute()
textView.setText("Hello !!!");//NullPointerException. textView.setText()被调用而没有初始化.

onPreExecute()
textView.setText("Hello !!!"); // NullPointerException. textView.setText() is called without initializing it.

警告

请勿在同一实例上多次呼叫AsyncTask.execute().
例如:

Do not call AsyncTask.execute() more than one on a same intance.
For eg:

DisplayMsgClass displayMsgClass = new DisplayMsgClass();  
displayMsgClass.execute();  
displayMsgClass.execute(); //Error, IllegalStateException  

将向您展示一个基于实现的基本演示，您可以根据自己的方式简单地对其进行修改.

will show you a basic demo based on you implementation and you can simply modify it according to your own way.

public void MethodTest() {

    // execute task
    new DisplayMsgClass().execute("Download now");
}

/*
public void MethodTest() {
    DisplayMsg("method 1 is running");
    Method1();

    DisplayMsg("method 2 is running");
    Method2();

    DisplayMsg("method 3 is running");
    Method3();

}

private int DisplayMsg(String msg) {
    totalMsg += msg;
    DisplayMsgClass dc = new DisplayMsgClass();
    dc.doInBackground(totalMsg);
}
*/

private class DisplayMsgClass extends AsyncTask<String, Integer, String> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();

        // retrieve the widgets
        progressBar = (ProgressBar) findViewById(R.id.progressBar1);
        textView = (TextView) findViewById(R.id.textv1);


        textView.setText("Download initialized");
        progressBar.setVisibility(View.VISIBLE);
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
    }

    @Override
    protected String doInBackground(String... Messages) {

        // read commands
        String command = Messages[0];
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "Download completed";
    }

    @Override
    protected void onPostExecute(String result) {

        //invoked on the UI thread after the background computation finishes
        progressBar.setVisibility(View.INVISIBLE);
        textView.setText(result);
    }
} 

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