當我離開活動時，爲什麼不保存我的文本？

Question

我有一個筆記應用程序，基本上我希望它可以保存文本輸入並在我返回活動時恢復它。但爲什麼我的代碼不是這樣做的？我嘗試過恢復實例狀態和onRestore，但它不起作用。任何人知道我可以保存文本輸入後，我退出應用程序？

notes.java：

public class notes extends Activity{ 




    /** Called when the activity is first created. */ 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.notes); 




     Button wg = (Button) findViewById(R.id.button3); 
     wg.setOnClickListener(new View.OnClickListener() { 
      public void onClick(View view) { 
       Intent intent = new Intent(); 
       setResult(RESULT_OK, intent); 
       finish(); 
      } 
     }); 

    } 
} 

Answer 1

確定這裏你已經工作，測試代碼

notes.java（src\izzy\n\notes.java）

package izzy.n; 

import android.app.Activity; 
import android.content.Context; 
import android.content.SharedPreferences; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.widget.EditText; 

// actually you should name the class "Notes" since it's convention 
// but it would proably cause errors since you have to rename the file then. 
public class notes extends Activity { 
    public static final String DEFAULT_TEXT = "Write some text here"; 
    public static final String PREFS_KEY_TEXT = "text"; 
    public static final String PREFS_NAME = "MyPrefsFile"; 

    private EditText mEditText; 

    /** 
    * Loads the text from SharedPreferences 
    */ 
    private String loadText() { 
     SharedPreferences settings = getSharedPreferences(notes.PREFS_NAME, 
       Context.MODE_PRIVATE); 
     return settings.getString(notes.PREFS_KEY_TEXT, notes.DEFAULT_TEXT); 
    } 

    /** 
    * Saves text to SharedPreferences 
    */ 
    private void saveText(String text) { 
     SharedPreferences settings = getSharedPreferences(notes.PREFS_NAME, 
       Context.MODE_PRIVATE); 
     SharedPreferences.Editor editor = settings.edit(); 
     editor.putString(notes.PREFS_KEY_TEXT, text); 
     editor.commit(); 
    } 

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.notes); 

     // when you click on the button the app will exit 
     // you kind of don't need such a button :) 
     Button wg = (Button) findViewById(R.id.exit_button); 
     wg.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       finish(); 
      } 
     }); 

     mEditText = (EditText) findViewById(R.id.edit_text); 

     String savedText = loadText(); 
     mEditText.setText(savedText); 
     // put the cursor to the end. 
     mEditText.setSelection(savedText.length()); 
    } 

    @Override 
    protected void onStop() { 
     super.onStop(); 
     saveText(mEditText.getText().toString()); 
    } 

} 

notes.xml（res\layout\notes.xml ）

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:orientation="vertical" > 

    <Button 
     android:id="@+id/exit_button" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:text="Exit" /> 

    <EditText 
     android:id="@+id/edit_text" 
     android:layout_width="match_parent" 
     android:layout_height="0dp" 
     android:gravity="top" 
     android:layout_weight="1" 
     android:hint="Enter Text here" 
     android:inputType="textMultiLine" /> 

</LinearLayout> 

你得到什麼

PS：你也許應該開始讀一些基本的Java教程因爲你似乎有基礎:)