Question

我正在开发一个应用程序，我必须实现一个按钮，当单击该按钮时，将开始图像下载，并出现progressDialog，其中包含一个显示图像下载进度的水平条。下载完成后，进度对话框将消失并显示图像。问题是，当下载正在进行时（显示progressDialog），如果我旋转我的屏幕，应用程序崩溃，我该如何解决这个问题？

这是我的代码：

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.res.Configuration;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivityProgress extends Activity {

    Button button;

    private ProgressDialog progressDialog;
    ImageView imageView;
    public static final int progress_bar_type = 0;

    private static String file_url = "http://farm1.static.flickr.com/114/298125983_0e4bf66782_b.jpg";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_activity_progress);

        button = (Button) findViewById(R.id.btnProgressBar);

        imageView = (ImageView) findViewById(R.id.my_image);

        button.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                new DownloadFileFromURL().execute(file_url);
            }
        });
    }

    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case progress_bar_type:
            progressDialog = new ProgressDialog(this);
            progressDialog.setMessage("Downloading file. Please wait...");
            progressDialog.setIndeterminate(false);
            progressDialog.setMax(100);
            progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            progressDialog.setCancelable(false);
            progressDialog.show();
            return progressDialog;
        default:
            return null;
        }
    }

   @Override
    public void onConfigurationChanged(Configuration newConfig){ 
            super.onConfigurationChanged(newConfig);
            setContentView(R.layout.activity_main_activity_progress);        
    }

    class DownloadFileFromURL extends AsyncTask<String, String, String> {
        @SuppressWarnings("deprecation")
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            showDialog(progress_bar_type);
        }

        @SuppressLint("SdCardPath")
        @Override
        protected String doInBackground(String... f_url) {
            int count;
            try {
                URL url = new URL(f_url[0]);
                URLConnection conection = url.openConnection();
                conection.connect();

                int lenghtOfFile = conection.getContentLength();

                InputStream input = new BufferedInputStream(url.openStream(), 8192);

                OutputStream output = new FileOutputStream("/sdcard/downloadedfile.jpg");

                byte data[] = new byte[1024];

                long total = 0;

                while ((count = input.read(data)) != -1) {
                    total += count;
                    publishProgress(""+(total*100)/lenghtOfFile);

                    output.write(data, 0, count);
                }

                output.flush();

                output.close();
                input.close();

            } catch (Exception e) {
                Log.e("Error: ", e.getMessage());
            }

            return null;
        }

        protected void onProgressUpdate(String... progress) {
            progressDialog.setProgress(Integer.parseInt(progress[0]));
       }

        @SuppressWarnings("deprecation")
        @Override
        protected void onPostExecute(String file_url) {
            dismissDialog(progress_bar_type);

            String imagePath = Environment.getExternalStorageDirectory().toString() + "/downloadedfile.jpg";
            imageView.setImageDrawable(Drawable.createFromPath(imagePath));
        }

    }
}

这些是我的logcat错误：

07-31 10:00:48.023: E/MoreInfoHPW_ViewGroup(20485): Parent view is not a TextView
07-31 10:00:49.658: E/MoreInfoHPW_ViewGroup(20485): Parent view is not a TextView
07-31 10:00:49.728: E/ViewRootImpl(20485): sendUserActionEvent() mView == null
07-31 10:00:50.753: E/MoreInfoHPW_ViewGroup(20485): Parent view is not a TextView
07-31 10:00:50.803: E/ViewRootImpl(20485): sendUserActionEvent() mView == null
07-31 10:00:52.688: E/MoreInfoHPW_ViewGroup(20485): Parent view is not a TextView
07-31 10:00:52.803: E/ViewRootImpl(20485): sendUserActionEvent() mView == null
07-31 10:00:52.803: E/ViewRootImpl(20485): sendUserActionEvent() mView == null
07-31 10:00:52.828: E/ViewRootImpl(20485): sendUserActionEvent() mView == null
07-31 10:01:01.018: E/AndroidRuntime(20485): FATAL EXCEPTION: main
07-31 10:01:01.018: E/AndroidRuntime(20485): Process: com.example.progressdownload, PID: 20485
07-31 10:01:01.018: E/AndroidRuntime(20485): java.lang.IllegalArgumentException: no dialog with id 0 was ever shown via Activity#showDialog
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.app.Activity.missingDialog(Activity.java:3214)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.app.Activity.dismissDialog(Activity.java:3199)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at com.example.progressdownload.MainActivityProgress$DownloadFileFromURL.onPostExecute(MainActivityProgress.java:121)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at com.example.progressdownload.MainActivityProgress$DownloadFileFromURL.onPostExecute(MainActivityProgress.java:1)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.os.AsyncTask.finish(AsyncTask.java:632)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.os.AsyncTask.access$600(AsyncTask.java:177)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.os.Handler.dispatchMessage(Handler.java:102)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.os.Looper.loop(Looper.java:157)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at android.app.ActivityThread.main(ActivityThread.java:5293)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at java.lang.reflect.Method.invokeNative(Native Method)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at java.lang.reflect.Method.invoke(Method.java:515)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
07-31 10:01:01.018: E/AndroidRuntime(20485):    at dalvik.system.NativeStart.main(Native Method)

感谢。

Answer 1

那是因为对话框将变为null。您可以使用两种不同的方式解决这些问题。

停止重新创建整个活动。即设定您可以通过在应用程序的清单文件中添加以下内容来避免活动重新创建。

机器人：configChanges = “取向| keyboardHidden |屏幕尺寸” 如下
```
<activity
    android:name=".your activity"
    android:configChanges="orientation|keyboardHidden|screenSize"
    android:label="@string/app_name" >
</activity>
```
像往常一样在onPreExecute / onPostExecute期间显示/关闭AsyncTask中的对话框，但在方向更改的情况下，在活动中创建/显示对话框的新实例并将其引用传递给任务。请参阅以下代码并执行必要的步骤。

公共类MainActivity扩展了Activity {

    private Button mButton;
    private MyTask mTask = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        MyTask task = (MyTask) getLastNonConfigurationInstance();
        if (task != null) {
            mTask = task;
            mTask.mContext = this;
            mTask.mDialog =  new ProgressDialog(MainActivityProgress.this);
            mTask.mDialog.setMessage("Please wait...");
            mTask.mDialog.setIndeterminate(false);
            mTask.mDialog.setMax(100);
            mTask.mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            mTask.mDialog.setCancelable(true);
            mTask.mDialog.show();
        }

        mButton = (Button) findViewById(R.id.button1);
        mButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                mTask = new MyTask(MainActivity.this);
                mTask.execute();
            }
        });
    }

    @Override
    public Object onRetainNonConfigurationInstance() {
        String str = "null";
        if (mTask != null) {
            str = mTask.toString();
            mTask.mDialog.dismiss();
        }
        Toast.makeText(this, str, Toast.LENGTH_SHORT).show();
        return mTask;
    }

    private class MyTask extends AsyncTask<Void, Void, Void> {
        private ProgressDialog mDialog;
        private MainActivity mContext;

        public MyTask(MainActivity context) {
            super();
            mContext = context;
        }

        protected void onPreExecute() {
                mDialog = new ProgressDialog(MainActivityProgress.this);
        mDialog.setMessage("Please wait...");
        mDialog.setIndeterminate(false);
        mDialog.setMax(100);
        mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        mDialog.setCancelable(true);
        mDialog.show();
        }

        protected void onPostExecute(Void result) {
            mContext.mTask = null;
            mDialog.dismiss();
        }

        @Override
        protected Void doInBackground(Void... params) {
            SystemClock.sleep(5000);
            return null;
        }
    }
}

好的，所以在编辑完代码后，它将如下所示：

公共类MainActivityProgress扩展了Activity {

Button button;

public static final int progress_bar_type = 0;

private static String file_url = "http://farm1.static.flickr.com/114/298125983_0e4bf66782_b.jpg";
private DownloadFileFromURL mTask = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_activity_progress);
    button = (Button) findViewById(R.id.btn_download);
    DownloadFileFromURL task = (DownloadFileFromURL) getLastNonConfigurationInstance();
    if (task != null) {
        mTask = task;
        mTask.mContext = this;
        mTask.mDialog = ProgressDialog.show(MainActivityProgress.this,
                "Downloading file.", "Please wait...", true);
    }

    button.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            mTask = new DownloadFileFromURL(MainActivityProgress.this);
            mTask.execute(file_url);
        }
    });
}

@Override
public Object onRetainNonConfigurationInstance() {
    String str = "null";
    if (mTask != null) {
        str = mTask.toString();
        mTask.mDialog.dismiss();
    }
    return mTask;
}

class DownloadFileFromURL extends AsyncTask<String, String, String> {

    private ProgressDialog mDialog;
    private MainActivityProgress mContext;

    public DownloadFileFromURL(MainActivityProgress context) {
        mContext = context;
    }

    protected void onPreExecute() {
        mDialog = ProgressDialog.show(MainActivityProgress.this,
                "Downloading file.", "Please wait...", true);
    }

    @Override
    protected String doInBackground(String... f_url) {
        SystemClock.sleep(5000);
        int count;
        try {
            URL url = new URL(f_url[0]);
            URLConnection conection = url.openConnection();
            conection.connect();

            int lenghtOfFile = conection.getContentLength();

            InputStream input = new BufferedInputStream(url.openStream(),
                    8192);

            OutputStream output = new FileOutputStream(
                    "/sdcard/downloadedfile.jpg");

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                publishProgress("" + (total * 100) / lenghtOfFile);

                output.write(data, 0, count);
            }

            output.flush();

            output.close();
            input.close();

        } catch (Exception e) {
            Log.e("Error: ", e.getMessage());
        }

        return null;
    }
     protected void onProgressUpdate(String... progress) {
         mDialog.setProgress(Integer.parseInt(progress[0]));
       }
    @Override
    protected void onPostExecute(String file_url) {
        mContext.mTask = null;
        if (mDialog.isShowing()) {
            mDialog.dismiss();
        }

        String imagePath = Environment.getExternalStorageDirectory()
                .toString() + "/downloadedfile.jpg";
        Log.e("imagePath: ", imagePath);
        // imageView.setImageDrawable(Drawable.createFromPath(imagePath));
    }

}

}

Answer 2

当您旋转设备系统时，系统会销毁之前方向的所有UI，并为新方向重新创建它。您可以阅读更多here。

所以我认为你应该在轮换时重新创建对话框。您可以在onConfigurationChanged方法中执行此操作。

Answer 3

    <activity
        android:name="com.example.one.MainActivityProgress"
        android:configChanges="orientation|screenSize"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

android：configChanges =“orientation | screenSize”在你的清单中做了你的问题解决了

Answer 4

查看this博客，了解有关如何处理方向更改的进度对话框的完整解决方案。希望它有所帮助。

progressDialog应用程序在屏幕旋转时崩溃

4 个答案: