在 Android 上缓存

Question

I have an app which gets data from Parse.com and uses in 2 sections, one in a listView and second in a grid view.

So I want to cache this data(Strings,bitmaps),to work offline, whenever the device won't have internet so it loads from cache. And whenever my app closed and opened again, it should update the cached data if there is internet. During the update if I have the same data in my cache it shouldn't create it again, it has to only create the new ones and update the views.

What is the best way to do this in android ?. Thanks.

Answer 1

For caching a data coming form Webservice

for Get a data u can use Volley or retrofit after getting an data you can set it to user desired attributes for caching the data both library giving the caching option for saving an data try to use that library.

Answer 2

To cache image you can use some library as: Glide, Picaso ... To cache text your need set up cache with HttpClient. Example:

private void configureCache() {
    if (cache == null)
        cache = createHttpClientCache(context);

    mHttpClient.setCache(cache);
    mHttpClient.networkInterceptors().add(REWRITE_CACHE_CONTROL_INTERCEPTOR);
}

private static Cache createHttpClientCache(Context context) {
    File cacheDir = context.getDir("cache_api", Context.MODE_PRIVATE);
    return new Cache(cacheDir, HTTP_CACHE_SIZE);
}

Answer 3

For String / Text :

1. If your data amount is not so much , you can use SharedPreference

2. If you have huge Data you should use SQlite

For Image :

1. Picasso -> http://square.github.io/picasso/

2. Universal Image Loader -> https://github.com/nostra13/Android-Universal-Image-Loader

Answer 4

try this code it will help-

File cacheDir = getBaseContext().getCacheDir();
File f = new File(cacheDir, "pic");

try {
    FileOutputStream out = new FileOutputStream(
            f);
    pic.compress(
            Bitmap.CompressFormat.JPEG,
            100, out);
    out.flush();
    out.close();

} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

Intent intent = new Intent(
        AndroidActivity.this,
        OpenPictureActivity.class);
startActivity(intent);

and then in the new activity-

public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    setContentView(R.layout.open_pic_layout);
    File cacheDir = getBaseContext().getCacheDir();
    File f = new File(cacheDir, "pic");     
    FileInputStream fis = null;
    try {
        fis = new FileInputStream(f);
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    Bitmap bitmap = BitmapFactory.decodeStream(fis);

    ImageView viewBitmap = (ImageView) findViewById(R.id.icon2);
    viewBitmap.setImageBitmap(bitmap);