This is a Util project for manage image and also solve OOM problems.
This project use LruCache，DiskLruCache , HttpUrlConnection , AsyncTask. And the layout use GridView and BaseAdapter.
The main running logic is
Bitmap bitmap = null;
bitmap = getInLruCache( httpUrlHashKey ); // get Bitmap object from LruCache
if( bitmap != null ) {
new SetImageView( bitmap , mViewHolder , position ); // if Bitmap is not null , set on ImageView
}else {
bitmap = getInDiskLruCache( httpUrlHashKey ); // get Bitmap object from DiskLruCache
if( bitmap != null ){
new SetImageView( bitmap , mViewHolder , position ); // if Bitmap is not null , set on ImageView
} else {
downLoadFromInternet( httpUrlString , mViewHolder , position ); // download image from the internet
}
}
All Classes's describe
| file name | describe |
|---|---|
| BitmapCalculateSize | resize the Bitmap object |
| BitmapManageHelper | set the input into Bitmap , use BitmapCalculateSize to resize and return a new Object |
| HashkeyMD5 | use MD5 to hash the image url into a new hashKey |
| ImageLruCacheManager | main image-manager class |
| GridViewAdapter | baseAdapter example |
| SetImageView | AsyncTask example |
| ViewHolder | ViewHolder example |
new ImageLruCacheManager class , extends BaseAdapter and Override getView(). And use this function in the getView()
getImage( String urlOfImage , ViewHolder CurrentViewHolder , int position );
you should define ViewHolder by your own situation.
- This project I also give a example by showing how Activity , BaseAdapter , ViewHolder should work.
- And a AsyncTask sub-class to set the ImageView
- ( But you can also use Handler + SoftReference , or Override runOnUiThread function in Activity
- sub-class to set the ImageView )
The example just a prototype of solving image-cache problems. Still,there's always things that can be improve.Such as :
- gridview cells overlapping.
- Use ThreadPoolExecutor class to manage the Thread.
- More effective to manage the thread and imageView from each item-View.
when we scroll from ListView/GridView/RecyclerView , we can add a flag when we scroll like 10 item , and user stil want to scroll down we release some bitmap resource or some resource that other Thread is using.
這個工具類將處理 Android 圖片問題，並且解決 OOM 問題。 雖然網路上有很多類似的專案在解決圖片問題，但是此工具類希望能讓核心邏輯整合的更完整的包裝。 並且我盡力將 Activity 和 Adapter 的 責任降至最低。
此工具類使用 LruCache，DiskLruCache，HttpUrlConnection，AsyncTask layout 上使用 GridView 以及 BaseAdapter
核心邏輯是
Bitmap bitmap = null;
bitmap = getInLruCache( httpUrlHashKey ); // 從 LruCache 當中獲取 Bitmap object
if( bitmap != null ) {
new SetImageView( bitmap , mViewHolder , position ); // 如果 Bitmap 不為空，設定在 ImageView上
}else {
bitmap = getInDiskLruCache( httpUrlHashKey ); // 從 DiskLruCache 當中獲取 Bitmap object
if( bitmap != null ){
new SetImageView( bitmap , mViewHolder , position ); // 如果 Bitmap 不為空，設定在 ImageView上
} else {
downLoadFromInternet( httpUrlString , mViewHolder , position ); // 從網路下載
}
}
所有類的解釋：
| 類名 | 描述 |
|---|---|
| BitmapCalculateSize | 根據現在螢幕的大小重新計算Bitmap的大小 |
| BitmapManageHelper | 將輸入或儲存物件轉化為Bitmap，用BitmapCalculateSize計算大小，並且重新輸出Bitmap |
| HashkeyMD5 | 將輸入的 Url 用 MD5 計算出雜湊碼 |
| ImageLruCacheManager | 主要的圖片執行類 |
| GridViewAdapter | baseAdapter 的範例 |
| SetImageView | AsyncTask 的範例 |
| ViewHolder | ViewHolder 的範例 |
實例化 ImageLruCacheManager 類 在 BaseAdapter 的子類複寫 getView(）方法，並且調用以下方法即可
getImage( String urlOfImage , ViewHolder CurrentViewHolder , int position );
其中的 ViewHolder 請根據您的情況自行定義
在這個 Project 當中我另外撰寫了 Activity + BaseAdapter + ViewHolder 和一個專門更新 UI 的 AsyncTask 類 ( 您也可以使用 Handler + SoftReference，或是在 Activity 裡面使用 runOnUiThread 來更新 UI )
專案內的使用範例只是一個最基本的使用原型而已。 我們還可以在某些地方加強邏輯：
- ImageView 重疊 / 錯位問題。
- 使用 ThreadPoolExecutor 來管理線程的創造和使用。
- 更有效的控管線程和每一個 imageView。 可以設計比如使用 ListView/GridView/RecyclerView 滑動到每第十個物件時 就釋放前面的 bitmap 資源或是 線程資源之類的。