Android P实现Bitmap、Byte[]数组和Drawable之间的相互转换

在安卓开发中，会经常用到将图片转化成byte[]数组保存或者传输，然后再将byte[]数组转换成图片格式，得到图片。

一、将图片转换成byte[]数组

public static byte[] bitmap2Bytes(Bitmap bitmap){
    if( null != bitmap ){
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);	//注意压缩png和jpg的格式和质量
        return baos.toByteArray();
    }
    return null;
}

二、将byte[]数组转换成bitmap

public static Bitmap bytes2Bitmap(byte[] bytes, BitmapFactory.Options opts){
    if ( null != opts ){
        return BitmapFactory.decodeByteArray(bytes, 0, bytes.length,opts);
    }else{
        return BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
    }
}

三、将byte[]数组转换成图片文件并保存起来

private void bytes2ImageFile(byte[] bytes) {
    try {
    	//将文件保存在路径“/storage/emulated/0/demo.jpg”
        File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/demo.jpg");
        FileOutputStream fos = new FileOutputStream(file);
        fos.write(bytes, 0, bytes.length);
        fos.flush();
        fos.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

四、将bitmap转换成drawable

public Drawable bitmap2Drawable(Bitmap bitmap){
	new BitmapDrawable(getResources(), bitmap)
}

关于静态方法使用getResources()报错的问题：Non-static method ‘getResources()’ cannot be referenced from a static context
解决：

private static Context mContext = null;
mContext = getActivity();
public Drawable bitmap2Drawable(Bitmap bitmap){
	new BitmapDrawable(mContext.getResources(), bitmap)
}

五、将drawable转换成bitmap

public Bitmap drawable2bitmap(Drawable drawable){
	new ((BitmapDrawable) drawable).getBitmap();
}