progressDialog应用程序在屏幕旋转时崩溃

debugcn 发表于 Dev

用户3783005

我正在一个必须实现按钮的应用程序上工作，单击该按钮时，将开始下载图像，并出现一个progressDialog，其中包含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），如果我旋转屏幕，应用程序将崩溃，请问如何解决此问题？

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)

谢谢。

用户名

那是因为对话将变为空。您可以使用两种不同的方法来解决这些问题。

停止重新创建整个活动。即设置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重新创建活动。

android：configChanges =“ orientation | keyboardHidden | screenSize”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，尽管在方向改变的情况下，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。请参考下面的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，因此在编辑代码后，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));
    }

}

}

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