首页 > 编程入门 文章详情

Android 异步任务进度条 onProgressUpdate

编程入门 行业动态 更新时间:2024-10-15 20:17:04
本文介绍了Android 异步任务进度条 onProgressUpdate的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我是一名新程序员.我看过很多教程，但不明白什么是错的.我正在尝试从异步任务创建一个 ProgressBar.但是它总是使我的应用程序崩溃.

I am a new programmer. I have seen lots of tutorials but can't understand what is wrong. I am trying to create a ProgressBar from an Async Task. However it always crashes my application.

这是主要"应用程序:

package pt.flag.ensemble; import java.util.Random; import pt.flag.ensemble.task.AsyncTaskBar; import android.app.Activity; import android.content.Context; import android.content.Intent; import android.content.SharedPreferences; import android.media.MediaPlayer; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.widget.Button; import android.widget.ImageButton; import android.widget.ProgressBar; import android.widget.Toast; public class Intervals extends Activity { private static Intervals instance; private Context context; private String answer; int right_question; int wrong_question; int randomInt2; public ProgressBar progressBar; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_intervals); // initializing the sounds final MediaPlayer sound1 = MediaPlayer.create(Intervals.this, R.raw.maj2); final MediaPlayer sound2 = MediaPlayer.create(Intervals.this, R.raw.maj3); final MediaPlayer sound3 = MediaPlayer.create(Intervals.this, R.raw.maj4); //ProgressBar instance=this; ProgressBar progressBar = (ProgressBar) findViewById(R.id.Progressbar); progressBar.setProgress(0); // Play Methods final ImageButton Play = (ImageButton) findViewById(R.id.Play); Play.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { new AsyncTaskBar().execute(); Play.setEnabled(false); // generate random number Random randomGenerator = new Random(); int randomInt = randomGenerator.nextInt(3) + 1; randomInt2 = randomInt; // picking the right sound to play switch (randomInt) { case 1: sound1.start(); answer = "M2"; break; case 2: sound2.start(); answer = "M3"; break; case 3: sound3.start(); answer = "P4"; break; } } }); //Audio Repeat Methods Button Repeat = (Button) findViewById(R.id.Repeat); Repeat.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { // picking the right sound to play switch (randomInt2) { case 1: sound1.start(); new AsyncTaskBar().execute(); answer = "M2"; break; case 2: sound2.start(); new AsyncTaskBar().execute(); answer = "M3"; break; case 3: sound3.start(); new AsyncTaskBar().execute(); answer = "P4"; break; } } }); } //Answering Methods public void buttonClicked2(View view) { Button clickedButton = (Button) view; if (clickedButton.getText().toString().equals(answer)) { Toast.makeText(Intervals.this, "You are Right!", Toast.LENGTH_LONG) .show(); right_question = right_question + 1; final ImageButton Play = (ImageButton) findViewById(R.id.Play); Play.setEnabled(true); // Passing results through SharedPreferences sharedPref = getSharedPreferences( "INTERVALRIGHTS", Context.MODE_PRIVATE); SharedPreferences.Editor editor = sharedPref.edit(); editor.putInt("SCORE", right_question); editormit(); } else { Toast.makeText(Intervals.this, "You are Wrong!", Toast.LENGTH_LONG) .show(); wrong_question = wrong_question + 1; // Passing results through SharedPreferences sharedPref02 = getSharedPreferences( "INTERVALWRONGS", Context.MODE_PRIVATE); SharedPreferences.Editor editor = sharedPref02.edit(); editor.putInt("SCORE02", wrong_question); editormit(); } } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.intervals, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. switch (item.getItemId()) { case R.id.action_settings: Intent intent = new Intent(Intervals.this, IntervalResults.class); startActivity(intent); break; default: return super.onOptionsItemSelected(item); } return true; } public static Intervals getApp() { return instance; } }

这里是 AsyncTask 类

Here is the AsyncTask class

package pt.flag.eventapp.task; import pt.flag.eventapp.Main; import android.os.AsyncTask; import android.os.SystemClock; import android.widget.Toast; public class ShowDialogAsyncTask extends AsyncTask<Void, Integer, Void> { int progress_status; @Override protected void onPreExecute() { // TODO Auto-generated method stub super.onPreExecute(); //Toast.makeText(Main.getApp(),"Invoke on PreExecute()", Toast.LENGTH_SHORT).show(); progress_status = 0 ; //Main.getApp().txt_percentage.setText("downloading 0%"); } @Override protected Void doInBackground(Void... params) { while (progress_status < 100){ progress_status +=2; publishProgress(progress_status); SystemClock.sleep(300); } return null; } @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); //Main.getApp().progressBar.setProgress(values[0]); //Main.getApp().txt_percentage.setText("downloading" + values[0] + "%"); } @Override protected void onPostExecute(Void result) { super.onPostExecute(result); //Toast.makeText(Main.getApp(), "Invoke onPostExecute()", Toast.LENGTH_SHORT).show(); //Main.getApp().txt_percentage.setText("download complete"); } }

这是日志:

08-10 20:38:11.081: E/AndroidRuntime(21441): FATAL EXCEPTION: main 08-10 20:38:11.081: E/AndroidRuntime(21441): java.lang.NullPointerException 08-10 20:38:11.081: E/AndroidRuntime(21441): at pt.flag.ensemble.task.AsyncTaskBar.onProgressUpdate(AsyncTaskBar.java:34) 08-10 20:38:11.081: E/AndroidRuntime(21441): at pt.flag.ensemble.task.AsyncTaskBar.onProgressUpdate(AsyncTaskBar.java:1) 08-10 20:38:11.081: E/AndroidRuntime(21441): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:618) 08-10 20:38:11.081: E/AndroidRuntime(21441): at android.os.Handler.dispatchMessage(Handler.java:99) 08-10 20:38:11.081: E/AndroidRuntime(21441): at android.os.Looper.loop(Looper.java:156) 08-10 20:38:11.081: E/AndroidRuntime(21441): at android.app.ActivityThread.main(ActivityThread.java:4977) 08-10 20:38:11.081: E/AndroidRuntime(21441): at java.lang.reflect.Method.invokeNative(Native Method) 08-10 20:38:11.081: E/AndroidRuntime(21441): at java.lang.reflect.Method.invoke(Method.java:511) 08-10 20:38:11.081: E/AndroidRuntime(21441): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 08-10 20:38:11.081: E/AndroidRuntime(21441): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 08-10 20:38:11.081: E/AndroidRuntime(21441): at dalvik.system.NativeStart.main(Native Method)

如果我是对的，日志似乎在 AsyncTask 类的第 34 行中指出了一个错误，即Intervals.getApp().progressBar.setProgress(values[0]);"我就是不知道为什么...

If I am correct, the log seems to indicate an error in line 34 at the AsyncTask class, which is "Intervals.getApp().progressBar.setProgress(values[0]);" I just don't know why...

另外，这是我的 xml 文件

Also, here is my xml file

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="schemas.android/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" > <ImageButton android:id="@+id/Play" android:contentDescription="@string/hello_world" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/ic_launcher" android:layout_marginTop="50dp" android:layout_marginLeft="50dp" /> <Button android:id="@+id/Repeat" android:contentDescription="@string/hello_world" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Repeat" android:layout_marginTop ="50dp" android:layout_toRightOf="@+id/Play" android:layout_marginLeft="25dp" /> <ProgressBar android:id="@+id/Progressbar" style="@android:style/Widget.ProgressBar.Horizontal" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="test" android:layout_marginTop="20dp" android:layout_below="@+id/Play" /> <Button android:id="@+id/Octave_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_marginLeft="5dp" android:layout_below="@+id/Progressbar" android:onClick="buttonClicked2" android:layout_marginTop="100dp" android:text="@string/octave" /> <Button android:id="@+id/min2_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Progressbar" android:onClick="buttonClicked2" android:layout_marginTop="100dp" android:layout_toRightOf="@+id/Octave_Button" android:text="@string/minor2" /> <Button android:id="@+id/Maj2_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Progressbar" android:onClick="buttonClicked2" android:layout_marginTop="100dp" android:layout_toRightOf="@+id/min2_Button" android:text="@string/major2" /> <Button android:id="@+id/min3_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Progressbar" android:onClick="buttonClicked2" android:layout_marginTop="100dp" android:layout_toRightOf="@+id/Maj2_Button" android:text="@string/minor3" /> <Button android:id="@+id/Maj3_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Progressbar" android:onClick="buttonClicked2" android:layout_marginTop="100dp" android:layout_toRightOf="@+id/min3_Button" android:text="@string/major3" /> <Button android:id="@+id/P4_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Progressbar" android:onClick="buttonClicked2" android:layout_marginTop="100dp" android:layout_toRightOf="@+id/Maj3_Button" android:text="@string/perfect4" /> <Button android:id="@+id/A4_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Octave_Button" android:onClick="buttonClicked2" android:layout_marginTop="15dp" android:layout_marginLeft="5dp" android:text="@string/tritone" /> <Button android:id="@+id/P5_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/min2_Button" android:onClick="buttonClicked2" android:layout_marginTop="15dp" android:layout_toRightOf="@+id/A4_Button" android:text="@string/perfect5" /> <Button android:id="@+id/minor6_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Maj2_Button" android:onClick="buttonClicked2" android:layout_marginTop="15dp" android:layout_toRightOf="@+id/P5_Button" android:text="@string/minor6" /> <Button android:id="@+id/Major6_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/min3_Button" android:onClick="buttonClicked2" android:layout_marginTop="15dp" android:layout_toRightOf="@+id/minor6_Button" android:text="@string/major6" /> <Button android:id="@+id/minor7_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/Maj3_Button" android:onClick="buttonClicked2" android:layout_marginTop="15dp" android:layout_toRightOf="@+id/Major6_Button" android:text="@string/minor7" /> <Button android:id="@+id/Major7_Button" android:layout_width="52dp" android:layout_height="80dp" android:layout_below="@+id/P4_Button" android:onClick="buttonClicked2" android:layout_marginTop="15dp" android:layout_toRightOf="@+id/minor7_Button" android:text="@string/major7" />

推荐答案

我认为将进度条作为参数传递给 AsyncTask 会更好:

I think it's better if you pass the progress bar as an argument to the AsyncTask:

final ProgressBar progressBar = (ProgressBar) findViewById(R.id.Progressbar); progressBar.setProgress(0); // Play Methods final ImageButton Play = (ImageButton) findViewById(R.id.Play); Play.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { AsyncTaskBar task = new AsyncTaskBar(); task.setProgressBar(progressBar); task.execute(); }

然后在你的 AsyncTask 上声明 setProgressBar 方法:

And then on your AsyncTask declare the setProgressBar method:

public class ShowDialogAsyncTask extends AsyncTask<Void, Integer, Void> { ProgressBar bar; public void setProgressBar(ProgressBar bar) { this.bar = bar; } @Override protected void onProgressUpdate(Integer... values) { super.onProgressUpdate(values); if (this.bar != null) { bar.setProgress(values[0]); } }

您可以对要设置的 TextView 执行相同的操作.

You could do the same with the TextView you're trying to set.

无论如何，既然你提到你是新手，你可能想看看广播/接收器模式.过程如下:

In any case, since you mentioned you're new at this you may want to take a look at the Broadcast/Receiver pattern. Here's how it goes:

  • 在不设置进度条或任何内容的情况下启动异步任务.
  • 定义一个 BroadcastReceiver，在您的 Activity 中实例化一个并相应地注册/取消注册.
  • 每当您的异步任务有进度更新时，只需将进度更新作为额外意图调用 sendBroadcast.实例化 AsyncTask 时，您可能需要传递上下文参数.
  • 您应用的广播接收器(您在第 2 步中实例化的那个)的 onHandleIntent 方法将在 UI 线程上运行，从而确保所有这些 UI 更新都是安全的.
  • Start the async task without setting the progress bar or anything.
  • Define a BroadcastReceiver, instantiate one in your activity and register/unregister it accordingly.
  • Whenever there's a progress update on your async task just call sendBroadcast with the progress update as an intent extra. You may need to pass a context parameter when instantiating the AsyncTask.
  • The onHandleIntent method of your app's broadcast receiver (the one you instantiated on step 2) will run on the UI thread, making all those UI updates safe.

    • 听起来有点不知所措?一开始是这样，但好处是:

    Sounds a bit overwhelming? It is at first, but here are the benefits:

  • 这比将 UI 对象传递给 AsyncTask 要简洁得多.
  • 您将学习一种强大的 Android 模式，该模式将在其他工作中派上用场.
  • 如果您切换上下文或您的应用内存不足，它将为您省去很多麻烦(和例外).

    • 更多推荐

    Android 异步任务进度条 onProgressUpdate

    本文发布于:2023-11-08 10:35:31，感谢您对本站的认可！
    本文链接:https://www.elefans.com/category/jswz/34/1569149.html
    版权声明:本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系，我们将在24小时内删除。
    本文标签：进度条   Android   onProgressUpdate

    发布评论

    评论列表 （有 0 条评论）

    最近发表

    草根站长

    >www.elefans.com

    编程频道|电子爱好者 - 技术资讯及电子产品介绍！

    热门文章

    标签列表