从 sd 卡创建一个可绘制对象以在 android 中设置为背景 [英] creating a drawable from sd card to set as a background in android

问题描述

我正在尝试使用 sd 卡中的图像并将其设置为相对布局的背景.我已经尝试过在这里和其他地方找到的其他解决方案，但它们似乎对我不起作用.这是我的代码.我已经评论了我尝试过但没有奏效的其他方法.唯一对我有用的是使用 setBackgroudnResource 并使用应用程序中的资源，但这只是为了测试以确保 mRoot 设置正确.当我尝试了所有其他方式时，它只是没有设置任何东西.任何人都知道我做错了什么，或者是否有更好的方法来做到这一点?

I am trying to use an image from the sd card and set it as the background for a relativelayout. I have tried other solutions that i have found here and elsewhere but they havent seemed to work for me. here is my code. I have commented out other ways that i have tried and didnt work. the only thing that worked for me was using setBackgroudnResource and using a resource from the app, but this was just to test to make sure mRoot was set up correctly. when I have tried all the other ways, it just doesn't set anything. Anyone know what I am doing wrong, or if there is a better way to do this?

        //one way i tired...
//String extDir = Environment.getExternalStorageDirectory().toString();
//Drawable d = Drawable.createFromPath(extDir + "/pic.png");
//mRoot.setBackgroundDrawable(d);

//another way tried..
//Drawable d = Drawable.createFromPath("/sdcard/pic.png");
//mRoot.setBackgroundDrawable(d);

//last way i tried...
mRoot.setBackgroundDrawable(Drawable.createFromPath(new File(Environment.getExternalStorageDirectory(), "pic.png").getAbsolutePath()));

//worked, only to verify mRoot was setup correctly and it could be changed
//mRoot.setBackgroundResource(R.drawable.bkg);

推荐答案

你不是从 SD 卡加载一个 drawable，而是一个位图.这是一种以减少采样(质量)加载它的方法，因此如果图像太大，程序不会抱怨.然后我猜你需要处理这个位图，即裁剪它并调整背景大小.

You do not load a drawable from SD card but a bitmap. Here is a method to load it with the reduced sampling (quality) so the program will not complain if the image is too large. Then I guess you need to process this bitmap i.e. crop it and resize for the background.

         // Read bitmap from Uri
     public Bitmap readBitmap(Uri selectedImage) {
         Bitmap bm = null;
         BitmapFactory.Options options = new BitmapFactory.Options();
         options.inSampleSize = 2; //reduce quality 
         AssetFileDescriptor fileDescriptor =null;
         try {
             fileDescriptor = this.getContentResolver().openAssetFileDescriptor(selectedImage,"r");
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         }
         finally{
             try {
                 bm = BitmapFactory.decodeFileDescriptor(fileDescriptor.getFileDescriptor(), null, options);
                 fileDescriptor.close();
             } catch (IOException e) {
                 e.printStackTrace();
             }
         }
         return bm;
     }

这里的 Uri 可以从画廊选择器活动中提供.

The Uri here can be supplied from a gallery picker activity.

然后可以将图像保存到应用程序资源中并加载到 imageView 中

The image then can be saved into application resources and loaded into an imageView

        private void saveBackground(Bitmap Background) {
        String strBackgroundFilename = "background_custom.jpg";
        try {
            Background.compress(CompressFormat.JPEG, 80, openFileOutput(strBackgroundFilename, MODE_PRIVATE));
        } catch (Exception e) {
            Log.e(DEBUG_TAG, "Background compression and save failed.", e);
        }

        Uri imageUriToSaveCameraImageTo = Uri.fromFile(new File(BackgroundSettings.this.getFilesDir(), strBackgroundFilename));

        // Load this image
        Bitmap bitmapImage = BitmapFactory.decodeFile(imageUriToSaveCameraImageTo.getPath());
        Drawable bgrImage = new BitmapDrawable(bitmapImage);

        //show it in a view
        ImageView backgroundView = (ImageView) findViewById(R.id.BackgroundImageView);
        backgroundView.setImageURI(null); 
        backgroundView.setImageDrawable(bgrImage);
    }

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