Android GridView - 如何动态更改位图？

Question

你好，我有一个 gridView，我用它来显示一些图片（不同级别的小拇指）。 当用户完成一个级别时，我想更改该级别的拇指。 （以某种方式表明它已经完成）。

我为每个级别创建了两个拇指。一张是原始的，一张是显示关卡已完成的。

但是如何更改图像的来源呢？

我用来绘制图像的代码如下所示。

主要活动：

/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.maps);

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

  gridview.setOnItemClickListener(new OnItemClickListener() {
    @Override
      public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
        //Open the map which was clicked on, if there is one
        if(position+1 > 1){
            Toast.makeText(maps.this, "Level " + (position+1) + " is not yet available!", Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(maps.this, "Opening Level " + (position+1), Toast.LENGTH_SHORT).show();
            Intent myIntent = new Intent(v.getContext(), Tutorial2D.class);
            startActivity(myIntent);
        }
      }
  });
}

ImageAdapter 类：

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;
    }

    //Changing
    imageView.setImageResource(mThumbIds[position]);
    return imageView;
}



// references to our images
private Integer[] mThumbIds = {
        R.drawable.map1, R.drawable.map2, R.drawable.map3,
        R.drawable.map4, R.drawable.map5, R.drawable.map6,
        R.drawable.map7, R.drawable.map8, R.drawable.map9,
        R.drawable.map10, R.drawable.map11, R.drawable.map12,
        R.drawable.map13, R.drawable.map14, R.drawable.map15,
        R.drawable.map16, R.drawable.map17, R.drawable.map18,
        R.drawable.map19
};

}

Answer 1

您可以根据拇指创建一个新的位图，并使用画布在其上绘制额外的图形。 将该位图传递给 imageview

然后你可以使用 imageView.setImageBitmap [edit]

[edit]类似

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;
    }

    if (mLevelfinished) {

        //create thumbnail bitmap
        mThumbBmp = BitmapFactory.decodeResource(mResources, mThumbIds[position]);

        //draw a check over the bitmap
        Canvas c = new Canvas(mThumbBmp);
        c.drawBitmap(mCheckBitmap, destX, destY, null);

        imageView.setImageBitmap(mThumbBmp);
    } else {
        imageView.setImageResource(mThumbIds[position]);
    }

    return imageView;
}

[edit2]

我现在发现我有点误解了你的问题.. doh。您已经拥有了这些拇指，而不是动态创建关卡完整拇指。在这种情况下，我将创建另一个包含这些已完成的拇指的数组，并从正确的数组中选择资源。为了坚持使用数组，也许也将关卡完成存储在一个数组中：

imageView.setImageResource((mLevelCompleted[position]) ? mThumbCompleteIds[position] : mThumbIds[position]);

Answer 2

我正在使用一个肮脏的技巧，当您事先知道将显示什么位图时，它可能会很有用。

我在可见的旁边设置了另一个不可见的ImageView，并操纵

myImageView.setVisibility(n); // (n = 0 = View.VISIBLE) or (n = 8 = View.GONE)

不要使用值为4的常量View.INVISIBLE，因为View.GONE 是正确的效果。当可见性设置为 View.GONE 时，该对象将不会占用布局中的空间。这类似于 CSS 中的 display: none;。

Answer 3

这是我所做的：

gridview.setAdapter(new ImageAdapter(this));
gridview.setOnItemClickListener(new OnItemClickListener() {
  public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
    Toast.makeText(Punch.this, "" + mThumbIds[position], Toast.LENGTH_SHORT).show();
     mThumbIds[position]=R.drawable.crabx;//crabxImg;

  //here is where I would like to redraw the whole grid but it will not let me. 
  //Because ImageAdapter is not defined within this callback.
  }
})