一、選擇圖片

定義Intent跳轉到特定相簿的Uri下挑選，然後將挑選結果返回給Activity

用到startActivityForResult

Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(intent, RESULT);

二、圖片縮放

這裡講的很詳細

照它所說有3種方法：

第一種是BitmapFactory和BitmapFactory.Options，同比例縮放，但是效率高

第二種是使用Bitmap加Matrix來縮放，能夠不同比例，但是效率低

第三種是用2.2新加的類ThumbnailUtils來做，這方法不懂，好複雜。。

我用第一種，將圖片放在Imageview中

  private void showPhoto(ImageView photo){
        String picturePath = target.getInfo(Target.TargetPhotoPath);// 圖片的uri
        if(picturePath.equals(""))
            return;
        // 縮放圖片, width, height 按相同比例縮放圖片
        BitmapFactory.Options options = new BitmapFactory.Options();
        // options 設為true時，構造出的bitmap沒有圖片，只有一些長寬等配置資訊，但比較快，設為false時，才有圖片
        options.inJustDecodeBounds = true;
        Bitmap bitmap = BitmapFactory.decodeFile(picturePath, options);
        int scale = (int)( options.outWidth / (float)300);
        if(scale <= 0)
            scale = 1;
        options.inSampleSize = scale;
        options.inJustDecodeBounds = false;
        bitmap = BitmapFactory.decodeFile(picturePath, options);

        photo.setImageBitmap(bitmap);
        photo.setMaxHeight(350);
    }
    
 

三、程式碼

public class RemindActivity extends Activity {

    private ImageView photo;
    private static final int RESULT = 1;
    Target target;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_remind);

        photo = (ImageView)findViewById(R.id.photo);
        target = new Target(this);

        showPhoto(photo);

        photo.setOnClickListener(new OnClickListener(){

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                Dialog dialog = new AlertDialog.Builder(RemindActivity.this)
                .setTitle("從相簿裡選擇照片").setMessage("確定要更換照片？").setPositiveButton("確定", 
                        new DialogInterface.OnClickListener() {

                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                // TODO Auto-generated method stub
                                Intent intent = new Intent(Intent.ACTION_PICK, android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                                startActivityForResult(intent, RESULT);
                            }
                        }).setNegativeButton("取消", new DialogInterface.OnClickListener() {

                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                // TODO Auto-generated method stub
                                dialog.cancel();
                            }
                        }).create();
                dialog.show();
            }

        });

    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // TODO Auto-generated method stub
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode == RESULT && resultCode == RESULT_OK && data != null){

            Uri selectedImage = data.getData();
            String[] filePathColumn = { MediaStore.Images.Media.DATA };

            Cursor cursor = getContentResolver().query(selectedImage,
                    filePathColumn, null, null, null);
            cursor.moveToFirst();

            int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
            String picturePath = cursor.getString(columnIndex);
            cursor.close();

            target.setInfo(Target.TargetPhotoPath, picturePath);

            showPhoto(photo);
        }
    }

    private void showPhoto(ImageView photo){
        String picturePath = target.getInfo(Target.TargetPhotoPath);
        if(picturePath.equals(""))
            return;
        // 縮放圖片, width, height 按相同比例縮放圖片
        BitmapFactory.Options options = new BitmapFactory.Options();
        // options 設為true時，構造出的bitmap沒有圖片，只有一些長寬等配置資訊，但比較快，設為false時，才有圖片
        options.inJustDecodeBounds = true;
        Bitmap bitmap = BitmapFactory.decodeFile(picturePath, options);
        int scale = (int)( options.outWidth / (float)300);
        if(scale <= 0)
            scale = 1;
        options.inSampleSize = scale;
        options.inJustDecodeBounds = false;
        bitmap = BitmapFactory.decodeFile(picturePath, options);

        photo.setImageBitmap(bitmap);
        photo.setMaxHeight(350);
    }
}