安卓中图片资源的获取和转换

//1，已将图片保存到drawable目录下

//通过图片id获得Drawable

Resource res=gerResource();
Drawable drawable=res.getDrawable(id);//id为R.drawable.图片名称

//通过图片id获得Bitmap

Resource res=gerResource();

Bitmap bitmap=BitmapFactory.decodeResource(res, id);

//若只知道图片的名称，可以通过图片的名称获得图片的id

//name:图片的名称 defType：图片的类型（png,jpeg),defPackage:工程的包名
int id =int id =res.getIdentifier(name, defType, defPackage);
//获得id之后可以根据你的需要来获得Bitmap或Drawable

//2,已将图片保存到assest目录下

//知道图片的名称，通过inputstream打开图片

AssetManager asm=getAssetMg();
InputStream is=asm.open(name);//name:图片的名称
//获得Drawable
Drawable da = Drawable.createFromStream(is, null);
//获得Bitmap
Bitmap bitmap=BitmapFactory.decodeStream(is);

//3,图片保存在sdcard,已知图片的路径

//图片路径
String path = Environment.getExternalStorageDirectory().toString()+ "/DCIM/device.png";
RandomAccessFile mMiniThumbFile；
File imgfile = new File(path);
try {
    mMiniThumbFile = new RandomAccessFile(imgfile, "rw");
} catch (IOException ex) {
// Open as read-only so we can at least read the existing
// thumbnails.
try {
mMiniThumbFile = new RandomAccessFile(imgfile, "r");
} catch (IOException ex2) {
// ignore exception
System.out.println(ex2.toString());
}
}
data= new byte[10553];
try {
mMiniThumbFile.seek(0);
int got = mMiniThumbFile.read(data, 0, 10552);
System.out.println("got="+got);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
System.out.println(e.toString());
}
if (data != null) {
//通过data获得bitmap
Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0,data.length);

 

 

    //最简单的方法

        String filepath = "/sdcard/paiyipai.jpg";
        Bitmap bm = BitmapFactory.decodeFile(filepath);

        //BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。
        BitmapDrawable bd=new BitmapDrawable(bm);
        ImageView.setBackgroundDrawable(bd);