无法在android中的活动之间传递位图 [英] Can not pass bitmap between activities in android

问题描述

我需要通过从其他活动中选择图像来动态更改活动的背景.并将选定的图像传递回调用活动，但是当我尝试获取图像时，它为空.这是我的代码.

I need to change background of the activity dynamically , by selecting an image from an other activity. and passing the selected image back to the calling activity , but when i try to get the image , it is null. here is my code.

  public class SelectGoalBackground extends OrmLiteBaseActivity<DatabaseHelper> {// implements{



GridView gridview ;
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.select_goal_background);
   final String from = getIntent().getExtras().getString("from");
    goalsList = new ArrayList<Goal>();

    try {
        goalsList = getTop3Goals();
    } catch (SQLException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } catch (java.sql.SQLException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }


     gridview = (GridView) findViewById(R.id.gridview);
    gridview.setAdapter(new ImageAdapter(this));

    gridview.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v, int position, long id) {

           ImageView l = (ImageView)gridview.getChildAt(position);
              Drawable path= l.getDrawable();


            Bitmap bitmap = ((BitmapDrawable)path).getBitmap();

            Intent intent = new Intent(SelectGoalBackground.this, AlarmAppActivity.class);

            intent.putExtra("Bitmap", bitmap);
            startActivity(intent);
            SelectGoalBackground.this.finish();
            return;

    });

}


public class ImageAdapter extends BaseAdapter {
    private Context mContext;

    public ImageAdapter(Context c) {
        mContext = c;
    }

    public int getCount() {
        return mThumbIds.length;
    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {  // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        } else {
            imageView = (ImageView) convertView;
        }
       Bitmap bm = BitmapFactory.decodeResource(getResources(), mThumbIds[position]);
        imageView.setImageBitmap(bm);
        return imageView;
    }

    // references to our images
    private Integer[] mThumbIds = {
            R.drawable.sample_0, R.drawable.sample_1

    };
}

在调用活动时我得到这样的位图

and in calling activity i get this bitmap like this

    RelativeLayout rel_lay = (RelativeLayout) findViewById(R.id.main_lay);
    Bitmap bitmap = (Bitmap)this.getIntent().getParcelableExtra("Bitmap");


    if (bitmap != null) {

        Log.v("bitmap", "not null");
        Drawable drawable = new BitmapDrawable(getResources(), bitmap);
        rel_lay.setBackgroundDrawable(drawable);
    }

但是这里的位图是空的，它没有设置这个活动的背景.任何形式的帮助表示赞赏，请帮助

but bitmap is null here and it is not setting background of this activity. any kind of help is appreciated , plz help

推荐答案

有 3 个解决方案可以解决此问题.

There are 3 Solutions to solve this issue.

1) 首先将图像转换为字节数组，然后传入 Intent，在下一个活动中从 Bundle 中获取字节数组并转换为图像(位图)并设置为 ImageView.

1) First Convert Image into Byte Array and then pass into Intent and in next activity get byte array from Bundle and Convert into Image(Bitmap) and set into ImageView.

将位图转换为字节数组:-

Convert Bitmap to Byte Array:-

Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
ByteArrayOutputStream stream = new ByteArrayOutputStream();
bmp.compress(Bitmap.CompressFormat.PNG, 100, stream);
byte[] byteArray = stream.toByteArray();

将字节数组传递给意图:-

Pass byte array into intent:-

Intent intent = new Intent(this, NextActivity.class);
intent.putExtra("picture", byteArray);
startActivity(intent);

从 Bundle 中获取字节数组并转换为位图图像:-

Get Byte Array from Bundle and Convert into Bitmap Image:-

Bundle extras = getIntent().getExtras();
byte[] byteArray = extras.getByteArray("picture");

Bitmap bmp = BitmapFactory.decodeByteArray(byteArray, 0, byteArray.length);
ImageView image = (ImageView) findViewById(R.id.imageView1);

image.setImageBitmap(bmp);

2) 首先将图像保存到 SDCard 中，然后在下一个活动中将此图像设置为 ImageView.

2) First Save image into SDCard and in next activity set this image into ImageView.

3) 将 Bitmap 传递到 Intent 并从 bundle 中获取下一个活动中的位图，但问题是如果当时您的 Bitmap/Image 尺寸很大，则图像不会在下一个活动中加载.

3) Pass Bitmap into Intent and get bitmap in next activity from bundle, but the problem is if your Bitmap/Image size is big at that time the image is not load in next activity.

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