java - 以编程方式清除所有 SdCard 文件

Question

我正在尝试执行清除外部 SdCard 中存在的所有文件的任务。

我没有找到我的代码无法正常工作的地方。

这些是我的文件...

activity-main.xml

    <?xml version="1.0" encoding="utf-8"?>

   <LinearLayout android:orientation="vertical" 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent"
     xmlns:android="http://schemas.android.com/apk/res/android">

    <Button android:id="@+id/wipe_button" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"
         android:text="Wipe the SD card." />

    <TextView android:id="@+id/path" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" />

    <TextView android:id="@+id/file" 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" />

</LinearLayout>

WipeSdActivity.java

package com.example.wipe_sd;

import java.io.File;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class WipeSDActivity extends Activity {

    private int mDeletedFiles = 0;
      private int mDeletedFolders = 0;

      private TextView mDirectoryTextView;
      private TextView mFileTextView;

      private List<String> mUndeleteableFiles;
      MyAsyncTask test;
      public Button btnwipe_sd;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_wipe_sd);

        btnwipe_sd = (Button)findViewById(R.id.wipe_button);


        test = new MyAsyncTask();

        File[] arrayOfFile = new File[1];
        arrayOfFile[0] = new File(Environment.getExternalStorageDirectory().getPath());
        test.execute(arrayOfFile);

        btnwipe_sd.setOnClickListener(new View.OnClickListener()
        {
              public void onClick(View paramAnonymousView)
              {
                new AlertDialog.Builder(WipeSDActivity.this).setCancelable(true)
                .setMessage("This will attempt to wipe all directories and files on your SD card.")
                .setPositiveButton("WIPE", new DialogInterface.OnClickListener()
                {
                  public void onClick(DialogInterface dialog, int which)
                  {

                  }
                }).setNegativeButton("NO!", new DialogInterface.OnClickListener()
                {
                  public void onClick(DialogInterface dialog, int which)
                  {
                    dialog.dismiss();
                  }
                }).show();
              }
            });

        this.mDirectoryTextView = ((TextView)findViewById(R.id.path));
        this.mFileTextView = ((TextView)findViewById(R.id.file));
        this.mUndeleteableFiles = new ArrayList();


    }

    public  class MyAsyncTask extends AsyncTask<File,Integer,Integer>{


        protected Integer doInBackground(File[] ArrayOfFile) {
            // TODO Auto-generated method stub
            int i = 0;
            progressivelyDelete(ArrayOfFile[0]);

            if (ArrayOfFile[0].exists())

                i = ArrayOfFile[0].listFiles().length;

            return Integer.valueOf(i);

        }

        private void progressivelyDelete(File sd_File) {
            // TODO Auto-generated method stub

             if (sd_File == null);

             while (true)
                 {

                         if (sd_File.isDirectory())
                         {
                             updateDirectory(sd_File.getPath());
                             File[] arrayOfFile = sd_File.listFiles();

                             int i = arrayOfFile.length;
                                int j = 0;
                                if (j < i)
                                {
                                    File msd_File = arrayOfFile[j];
                                    if (msd_File.canWrite())
                                      progressivelyDelete(msd_File);

                                    while (true)
                                    {
                                        j++;
                                        break;

                                    }
                                    WipeSDActivity.this.mUndeleteableFiles.add(msd_File.getAbsolutePath());
                                }


                                sd_File.delete();
                         }
                         else 
                         {
                            sd_File.delete();
                            updateFile(sd_File.getName());

                         }
                 }  
        }

        private void updateFile(final String paramString) {
            // TODO Auto-generated method stub
             Log.d("SdWipe", "File - " + paramString);

             WipeSDActivity.this.runOnUiThread(new Runnable() {

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

                    TextView localfile_TextView = WipeSDActivity.this.mFileTextView;
                    Object[] arrayofObject = new Object[1];

                    arrayofObject[0] = paramString;


                }
            });

        }

        private void updateDirectory(final String paramString) {
            // TODO Auto-generated method stub

            Log.d("SdWipe", "Folder - " + paramString);
            WipeSDActivity.this.runOnUiThread(new Runnable() {

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

                    TextView localdir_TextView = WipeSDActivity.this.mDirectoryTextView;
                    Object[] arrayOfObject = new Object[1];
                    arrayOfObject[0] = paramString;

                    localdir_TextView.setText(String.format("Currently processing\n%s", arrayOfObject));

                }
            });

        }

        protected void onPostExecute(Integer paramInteger)
          {

            TextView dir_textview = WipeSDActivity.this.mDirectoryTextView;
            Object[] arrayOfObject = new Object[2];

            arrayOfObject[0] = Integer.valueOf(WipeSDActivity.this.mDeletedFolders);
            arrayOfObject[1] = Integer.valueOf(WipeSDActivity.this.mDeletedFiles);

            dir_textview.setText(String.format("Done\n%s folders deleted\n%s files deleted",arrayOfObject));

             StringBuilder localStringBuilder = new StringBuilder();
             Iterator localIterator = WipeSDActivity.this.mUndeleteableFiles.iterator();

             while(localIterator.hasNext())
             {
                 String str = (String) localIterator.next();

                 localStringBuilder.append(str + "\n");

             }
             WipeSDActivity.this.mFileTextView.setText(paramInteger + "files left on SD Card:\n" + localStringBuilder);

          }


        protected void onPreExecute()
                {

                    WipeSDActivity.this.mUndeleteableFiles.clear();
                }



    }

}

list .xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.wipe_sd"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.wipe_sd.WipeSDActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

我得到的 Log Cat 错误是:

02-08 16:47:13.460: E/AndroidRuntime(270): java.lang.RuntimeException: Unable to start activity 
ComponentInfo{com.example.wipe_sd/com.example.wipe_sd.WipeSDActivity}: java.lang.NullPointerException
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.os.Handler.dispatchMessage(Handler.java:99)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.os.Looper.loop(Looper.java:123)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.app.ActivityThread.main(ActivityThread.java:4627)
02-08 16:47:13.460: E/AndroidRuntime(270):  at java.lang.reflect.Method.invokeNative(Native Method)
02-08 16:47:13.460: E/AndroidRuntime(270):  at java.lang.reflect.Method.invoke(Method.java:521)
02-08 16:47:13.460: E/AndroidRuntime(270):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
02-08 16:47:13.460: E/AndroidRuntime(270):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
02-08 16:47:13.460: E/AndroidRuntime(270):  at dalvik.system.NativeStart.main(Native Method)
02-08 16:47:13.460: E/AndroidRuntime(270): Caused by: java.lang.NullPointerException
02-08 16:47:13.460: E/AndroidRuntime(270):  at com.example.wipe_sd.WipeSDActivity$MyAsyncTask.onPreExecute(WipeSDActivity.java:204)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.os.AsyncTask.execute(AsyncTask.java:391)
02-08 16:47:13.460: E/AndroidRuntime(270):  at com.example.wipe_sd.WipeSDActivity.onCreate(WipeSDActivity.java:44)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-08 16:47:13.460: E/AndroidRuntime(270):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
02-08 16:47:13.460: E/AndroidRuntime(270):  ... 11 more

Answer 1

我在这里修改了 WipeSDActivity.java 类。请检查并告诉我。希望它对您有所帮助。谢谢。

import java.io.File;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class WipeSDActivity extends Activity {

      private static ProgressDialog progressBar;
      private static int progressBarStatus = 0;
      private static Handler progressBarHandler = new Handler();      
      public Button btnwipe_sd;
      private int fileCount = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.sd_card);

    btnwipe_sd = (Button)findViewById(R.id.wipe_button);
    btnwipe_sd.setOnClickListener(new OnClickListener()
    {
          public void onClick(final View view)
          {

              new AlertDialog.Builder(WipeSDActivity.this).setCancelable(true)
              .setMessage("This will attempt to wipe all directories and files on your SD card.")
              .setPositiveButton("WIPE", new DialogInterface.OnClickListener()
              {
                public void onClick(DialogInterface dialog, int which)
                {
                  dialog.dismiss();
                  FormatSDCard(view);
                }
              }).setNegativeButton("NO!", new DialogInterface.OnClickListener()
              {
                public void onClick(DialogInterface dialog, int which)
                {
                  dialog.dismiss();
                }
              }).show();
          }
        });
    }


    public void FormatSDCard(View v){
        progressBar = new ProgressDialog(v.getContext());
        progressBar.setCancelable(false);
        progressBar.setMessage("File deleting ...");
        progressBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        progressBar.setProgress(0);
        progressBar.setMax(100);
        progressBar.show();

        new Thread(new Runnable() {
            public void run() {
                while (progressBarStatus < 100) {
                    //fileCount = 0;
                    // process some tasks
                    progressBarStatus = wipingSdcard();
                    // your computer is too fast, sleep 1 second
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    // Update the progress bar
                    progressBarHandler.post(new Runnable() {
                        public void run() {
                            progressBar.setProgress(progressBarStatus);
                        }
                    });
                }

                // ok, file is deleted,
                if (progressBarStatus >= 100) {

                    // sleep 2 seconds, so that you can see the 100%
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    // close the progress bar dialog
                    progressBar.dismiss();
                }
            }
        }).start();     
    }


    public int wipingSdcard() {
    File deleteMatchingFile = new File(Environment
            .getExternalStorageDirectory().toString());
    try {
        File[] filenames = deleteMatchingFile.listFiles();
        if (filenames != null && filenames.length > 0) {
            for (File tempFile : filenames) {
                if (tempFile.isDirectory()) {
                    wipeDirectory(tempFile.toString());
                    tempFile.delete();
                } else {
                    tempFile.delete();
                }
                fileCount++;
                progressBarStatus = fileCount;

                    progressBarHandler.post(new Runnable() {
                        public void run() {
                            progressBar.setProgress(progressBarStatus);
                        }
                    });
            }
        } else {
            deleteMatchingFile.delete();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
        return fileCount;
    }

    private void wipeDirectory(String name) {
    File directoryFile = new File(name);
    File[] filenames = directoryFile.listFiles();
    if (filenames != null && filenames.length > 0) {
        for (File tempFile : filenames) {
            if (tempFile.isDirectory()) {
                wipeDirectory(tempFile.toString());
                tempFile.delete();
            } else {
                tempFile.delete();
            }
        }
    } else {
        directoryFile.delete();
    }
    }
}

如果你使用 >1.6 SDK，你还必须授予权限

 <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

在AndroidManifest.xml文件中