无法以编程方式清除缓存内存 Android

Question

我已尝试使用以下代码通过应用程序中的按钮清除缓存。
activity_main.xml

 <LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:id="@+id/textView" />

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/editText" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Save"
        android:id="@+id/button" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Delete Cache"
        android:id="@+id/button2" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Retrive Data"
        android:id="@+id/button3" />
</LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity  {
TextView t1;
EditText et1;
Button b1,b2,b3;
public static final String PREFS_NAME = "MyPrefsFile";
SharedPreferences settings;
SharedPreferences.Editor editor;
private static MainActivity instance;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    settings = getSharedPreferences(MainActivity.PREFS_NAME, 0);
    editor= settings.edit();
    instance=this;
    t1=(TextView)findViewById(R.id.textView);
    et1=(EditText)findViewById(R.id.editText);
    b1=(Button)findViewById(R.id.button);
    b2=(Button)findViewById(R.id.button2);
    b3=(Button)findViewById(R.id.button3);
    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            editor.putString("editText",et1.getText().toString());
            editor.commit();
            t1.setText(settings.getString("editText",null));
        }
    });
    b2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            t1.setText("");
            MainActivity.getInstance().clearApplicationData();
                        }
    });
    b3.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            t1.setText(settings.getString("editText",null));
        }
    });
}
public static MainActivity getInstance(){ return instance;}
public void clearApplicationData(){
        File cache= getCacheDir();
        File appDir=new File(cache.getParent());
        if(appDir.exists()){
            String[] children = appDir.list();
            for(String s: children){
                if(!s.equals("lib")){
                    deleteDir(new File(appDir,s));
                    Log.i("TAG", "File /data/data/APP_PACKAGE/ " + s +" DELETED");
                }
            }
        }
}
public static boolean deleteDir(File dir) {
    if (dir != null && dir.isDirectory()) {
        String[] children = dir.list();
        for (int i = 0; i < children.length; i++) {
            boolean success = deleteDir(new File(dir, children[i]));
            if (!success) {
                return false;
            }
        }
        return dir.delete();
    }
    else {
        return false;
    }
}}

说明：
当点击 Save 按钮时，EditText 中输入的值将保存在 Shared Preference 中。点击 Delete Cache 时，编写删除缓存的代码与@987654321 @,Refer 2。当点击Retrive时，存储在Shared Preference中的值将被检索并显示在TextView中。

问题：在我的 logcat 中单击 Delete Cache 时，它显示 缓存内存已删除 并且 shared_prefs 已删除但我的缓存大小没有减少。在点击 Retrive 时，Shared Preference 中的值正在检索并显示在 TextView 中，但应该删除该值。

我的日志猫：

01-09 17:02:26.872 24290-24290/? I/TAG: File /data/data/APP_PACKAGE/ cache DELETED
01-09 17:02:26.872 24290-24290/? I/TAG: File /data/data/APP_PACKAGE/ shared_prefs DELETED

我错过了什么？

Answer 1

onStop() 和 onDestroy() 方法包含在您的 Activity 中。您的 Activity onDestroy() 添加以下代码

 @Override
  protected void onStop(){
  super.onStop();
   }
 // after the OnStop() state


  @Override
  protected void onDestroy() {
  super.onDestroy();
  try {
     trimCache(this);
      } catch (Exception e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
     }
   }

然后添加以下方法

 public static void trimCache(Context context) {
  try {
     File dir = context.getCacheDir();
     if (dir != null && dir.isDirectory()) {
        deleteDir(dir);
     }
  } catch (Exception e) {
     // TODO: handle exception
  }
 }

 public static boolean deleteDir(File dir) {
  if (dir != null && dir.isDirectory()) {
     String[] children = dir.list();
     for (int i = 0; i < children.length; i++) {
        boolean success = deleteDir(new File(dir, children[i]));
        if (!success) {
           return false;
        }
     }
  }

  // The directory is now empty so delete it
  return dir.delete();
 }