如何保存一個活動的狀態

Question

我有一個像下面這樣的活動。在這個活動中，我有超過10張圖片。圖像隨着下一個和後退按鈕而改變。我想保存這個活動的狀態。例如，如果我處於第5張圖片並關閉了該活動或應用程序。現在，當我開始活動或應用程序時，它從第一張圖片開始，而不是從第五張圖片開始。它應該從我已經離開它的第五張圖像開始。請幫助我編寫代碼或編輯我的代碼。

int[] images = { R.drawable.r1, R.drawable.r2, R.drawable.r3, R.drawable.r4, R.drawable.r5, R.drawable.r6, R.drawable.r7, R.drawable.r8, R.drawable.r9, R.drawable.r10 /// so on}; 
    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

    hImageViewPic = (ImageView)findViewById(R.id.idImageViewPic); 
    iButton = (Button) findViewById(R.id.bNext); 
    gButton = (Button) findViewById(R.id.bPrev); 
     //Just set one Click listener for the image 
    iButton.setOnClickListener(iButtonChangeImageListener); 
    gButton.setOnClickListener(gButtonChangeImageListener); 
    } 
    View.OnClickListener iButtonChangeImageListener = new OnClickListener() { 
     public void onClick(View v) { 
    //Increase Counter to move to next Image 
     currentImage++; 
     currentImage = currentImage % images.length; 
     hImageViewPic.setImageResource(images[currentImage]); 
     } 
    }; 
    View.OnClickListener gButtonChangeImageListener = new OnClickListener() { 
    public void onClick(View v) { 
    //Increase Counter to move to next Image 
    currentImage--; 
    currentImage = (currentImage + images.length) % images.length; 
    hImageViewPic.setImageResource(images[currentImage]); 
    } 
    }; 

請注意代碼。

Answer 1

int currentImage; 
    int[] images = { R.drawable.r1, R.drawable.r2, R.drawable.r3, R.drawable.r4, R.drawable.r5, R.drawable.r6, R.drawable.r7, R.drawable.r8, R.drawable.r9, R.drawable.r10 /// so on}; 
    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

    SharedPreferences settings = this.getSharedPreferences("imageNumber", 0); 
    if(settings != null){ 
      currentImage= settings .getInt("lastImage", 0); 
    } 
    hImageViewPic = (ImageView)findViewById(R.id.idImageViewPic); 
    iButton = (Button) findViewById(R.id.bNext); 
    gButton = (Button) findViewById(R.id.bPrev); 
     //Just set one Click listener for the image 
    iButton.setOnClickListener(iButtonChangeImageListener); 
    gButton.setOnClickListener(gButtonChangeImageListener); 
    } 
    View.OnClickListener iButtonChangeImageListener = new OnClickListener() { 
     public void onClick(View v) { 
    //Increase Counter to move to next Image 
     currentImage++; 
     currentImage = currentImage % images.length; 
     hImageViewPic.setImageResource(images[currentImage]); 
     } 
    }; 
    View.OnClickListener gButtonChangeImageListener = new OnClickListener() { 
    public void onClick(View v) { 
    //Increase Counter to move to next Image 
    currentImage--; 
    currentImage = (currentImage + images.length) % images.length; 
    hImageViewPic.setImageResource(images[currentImage]); 
    } 
    }; 

在的onPause方法：

@Override 
protected void onPause(){ 
    super.onPause(); 
    SharedPreferences settings = getSharedPreferences("imageNumber", 0); 
    SharedPreferences.Editor editor = settings.edit(); 
    editor.putInt("lastImage",currentImage ); 
    editor.commit(); 
} 

Answer 2

嘗試使用SharedPreferences來存儲您的上一個圖像位置。

private ImageView hImageViewPic; 
    private Button iButton; 
    private Button gButton; 

    private SharedPreferences sharedPreferences; 

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

     hImageViewPic = (ImageView) findViewById(R.id.idImageViewPic); 
     iButton = (Button) findViewById(R.id.bNext); 
     gButton = (Button) findViewById(R.id.bPrev); 

     sharedPreferences = getSharedPreferences(getString(R.string.app_name), MODE_PRIVATE); 

     hImageViewPic.setImageResource(images[sharedPreferences.getInt("LastSeenImagePosition", 0)]); 
     //Just set one Click listener for the image 
     iButton.setOnClickListener(iButtonChangeImageListener); 
     gButton.setOnClickListener(gButtonChangeImageListener); 
    } 
    View.OnClickListener iButtonChangeImageListener = new OnClickListener() { 
     public void onClick(View v) { 
      //Increase Counter to move to next Image 
      currentImage++; 
      currentImage = currentImage % images.length; 
      hImageViewPic.setImageResource(images[currentImage]); 
      SharedPreferences.Editor editor = sharedPreferences.edit(); 
      editor.putBoolean("LastSeenImagePosition", currentImage); 
      editor.commit(); 
     } 
    }; 
    View.OnClickListener gButtonChangeImageListener = new OnClickListener() { 
     public void onClick(View v) { 
      //Increase Counter to move to next Image 
      currentImage--; 
      currentImage = (currentImage + images.length) % images.length; 
      hImageViewPic.setImageResource(images[currentImage]); 
      SharedPreferences.Editor editor = sharedPreferences.edit(); 
      editor.putBoolean("LastSeenImagePosition", currentImage); 
      editor.commit(); 
     } 
    }; 

Answer 3

以上建議可以工作，但要做到這一點的方法是使用活動的 - 和的onSaveInstanceState onRestoreInstanceState。你可以看一下在這個例子： Saving Android Activity state using Save Instance State

或者在Android手冊閱讀：http://developer.android.com/reference/android/app/Activity.html#onSaveInstanceState(android.os.Bundle)

主要優點是值只保存真正需要的時候。