如何在 Gridview 上保留图像？请某人

Question

我有下面的代码，它将从图库中挑选出的图像列表放入 GridView 布局。 图片在 GridView 布局中显示得很好，但问题是当我关闭应用程序或从图库中选择不同图片时这些图片会消失。

有人能指点我正确的方向吗？

任何帮助将不胜感激。

代码：

public class MainActivity extends Activity {

   GridView gridGallery;
   Handler handler;
   Gallery_Adapter_Activity adapter;

   Button btnGalleryPick;
   Button btnGalleryPickMul;

   String action;
   ViewSwitcher viewSwitcher;
   ImageLoader imageLoader;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setContentView(R.layout.main);

    initImageLoader();
    init();
}

private void initImageLoader() {
    @SuppressWarnings("deprecation")
    DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder()
            .cacheOnDisc().imageScaleType(ImageScaleType.EXACTLY_STRETCHED)
            .bitmapConfig(Bitmap.Config.RGB_565).build();
    ImageLoaderConfiguration.Builder builder = new ImageLoaderConfiguration.Builder(
            this).defaultDisplayImageOptions(defaultOptions).memoryCache(
            new WeakMemoryCache());

    ImageLoaderConfiguration config = builder.build();
    imageLoader = ImageLoader.getInstance();
    imageLoader.init(config);
}

private void init() {

    handler = new Handler();
    gridGallery = (GridView) findViewById(R.id.gridGallery);
    gridGallery.setFastScrollEnabled(true);                     
    adapter = new Gallery_Adapter_Activity(getApplicationContext(), imageLoader);
    adapter.setMultiplePick(false);
    gridGallery.setAdapter(adapter);

    viewSwitcher = (ViewSwitcher) findViewById(R.id.viewSwitcher);
    viewSwitcher.setDisplayedChild(1);


    Button done_button = (Button) findViewById(R.id.done);      
    done_button.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {       
            finish();                           
        }                       
    });


    btnGalleryPickMul = (Button) findViewById(R.id.btnGalleryPickMul);
    btnGalleryPickMul.setOnClickListener(new View.OnClickListener() {                               

        @Override
        public void onClick(View v) {       //Add Images Button OnClickListener
            Intent i = new Intent(Multiple_Pick_Activity.ACTION_MULTIPLE_PICK);
            startActivityForResult(i, 12345);           
        }                           
    });

}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);

if (requestCode == result_requestcode && resultCode == Activity.RESULT_OK)

{       

SDcardPath_Activity SDcardPath_Class = new SDcardPath_Activity();

String[] ALL_Paths = data.getStringArrayExtra("all_path");

for (String single_path : ALL_Paths) 
{      

    SQ_LITE_DATABASE.addImageFile(single_path);           

}

try { 


ArrayList<SDcardPath_Activity> SQLite_Databse_Data = SQ_LITE_DATABASE.readImageFiles();
SQLite_Databse_Data.add(SDcardPath_Class);

viewSwitcher.setDisplayedChild(0);
adapter.addAll(SQLite_Databse_Data);        

Intent intent = new Intent (Image_MainActivity.this, Image_MainActivity.class);
startActivity(intent);
finish();

  } catch (Exception e) 
  {
   e.printStackTrace();
   return;

  }
 }       
}

编辑：发布上面的工作代码

Answer 1

把这些放在你的 onActivityResult 中：

  @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);

if (requestCode == result_requestcode && resultCode == Activity.RESULT_OK)

    {       

    SDcardPath_Activity SDcardPath_Class = new SDcardPath_Activity();

    String[] ALL_Paths = data.getStringArrayExtra("all_path");

    for (String single_path : ALL_Paths) 
    {      

        SQ_LITE_DATABASE.addImageFile(single_path);           

    }

 try { 


    ArrayList<SDcardPath_Activity> SQLite_Databse_Data = SQ_LITE_DATABASE.readImageFiles();
    SQLite_Databse_Data.add(SDcardPath_Class);

    viewSwitcher.setDisplayedChild(0);
    adapter.addAll(SQLite_Databse_Data);        

    Intent intent = new Intent (Image_MainActivity.this, Image_MainActivity.class);
    startActivity(intent);
    finish();

   } catch (Exception e) 
   {
    e.printStackTrace();
    return;

   }
  }       
 }

Answer 2

我建议您使用SQlite database 来存储图像路径。
拍照时，将它们保存在SD卡中，并在数据库中记录它们的路径。
每次您开始 Activity 时都会迭代您的数据库，获取所有内容并填充您的 GridView。
SharedPreferences 如果您不打算保存大量图像，这很好。

Answer 3

如果您需要在应用关闭时保留列表，则需要将列表存储到 SharedPreferences，数据库或文件。

方法一：使用 SharedPreferences。

将选定的文件保存到 SharedPreferences

 // selectedFiles is Set<String> with all your selected files
 Set<String> selectedFiles = new HashSet<String>();

 // TODO put your selected file names into selectedFiles set

 SharedPreferences prefs = getSharedPreferences("prefs_selection", 0);
 SharedPreferences.Editor editor = prefs.edit();

 editor.putStringSet("selection", selectedFiles);

 // save
 editor.commit();

从 SharedPreferences 中恢复选定的文件

SharedPreferences prefs = getSharedPreferences("prefs_selection", 0);

Set<String> selectedFiles = prefs.getStringSet("selection", null);
if (selectedFiles != null) {
    // TODO put elements of selectedFiles into appropriate your elements
}

方法二：使用 SQLLiteDatabase。

定义派生自 SQLiteOpenHelper 的类。

public class ImagesOpenHelper extends SQLiteOpenHelper {

    private static final String KEY_IMAGE = "image_file";
    private static final String DATABASE_NAME = "imagesdb";
    private static final int DATABASE_VERSION = 1;
    private static final String IMAGES_TABLE_NAME = "images";
    private static final String IMAGES_TABLE_CREATE =
            "CREATE TABLE " + IMAGES_TABLE_NAME + " (" +
            KEY_IMAGE + " TEXT);";

    public ImagesOpenHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(IMAGES_TABLE_CREATE);
    }

    public void addImageFile(String file) {
        ContentValues values = new ContentValues();
        values.put(KEY_IMAGE, file);

        getWritableDatabase().insert(IMAGES_TABLE_NAME, null, values);
    }

    public void readImageFiles() {
        Cursor cursor = getReadableDatabase().query(IMAGES_TABLE_NAME, new String[] { KEY_IMAGE }, null, null, null, null, null, null);

        try {
            if (!cursor.moveToFirst())
                return ; 

            ArrayList<SDcardPath_Activity> Picture_List = new ArrayList<SDcardPath_Activity>();

            do {
                String file = cursor.getString(0);

                SDcardPath_Activity PICTURE = new SDcardPath_Activity();
                PICTURE.sdcardPath = file;
                Picture_List.add(PICTURE);

            } while (cursor.moveToNext());

            viewSwitcher.setDisplayedChild(0);
            adapter.addAll(Picture_List);
        }
        finally {
            cursor.close();
        }
    }
}

在activity的onCreate中创建这个类的对象。 调用 readImageFiles() 读取图像文件路径。 调用 addImageFile(String file) 将图像文件路径添加到数据库中。

在 ImageLoader imageLoader 行之后添加以下行：

ImagesOpenHelper imagesOpenHelper;

添加到 onCreate

imagesOpenHelper = new ImagesOpenHelper(this);
imagesOpenHelper.readImageFiles();

在 onActivityResult 中将以下行添加到 for 循环中：

imagesOpenHelper.addImageFile(string);