java - Android Activity 上下文为空

Question

所以我这里有这些代码，它运行时不会崩溃。但是，当我将“this”传递到网格适配器时，mContext 为空。我尝试传递 getApplicationContext() 但仍然无法使 getImage 方法正常运行，因为 getResources.getIdentifier 行不会返回任何内容，因为 Context 为空。如果有人能教我为什么会发生这种情况以及如何解决它，我将不胜感激。谢谢。

public class ChampionInfo extends FragmentActivity {

GridView gridtable;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_champion_info);

    gridtable = (GridView) findViewById(R.id.gridtable);        
    gridtable.setAdapter(new GridAdapter(getApplicationContext()));

}

public class GridAdapter extends BaseAdapter {
    private Context mContext;

    String[] list = getResources().getStringArray(R.array.championlist);

    int[] champImage = getImage();

    public int[] getImage() {

        int[] tempImage = new int[list.length];

        for (int i = 0; i < list.length; i++) {
            tempImage[i] = getResources().getIdentifier(list[i],
                    "drawable", getPackageName());
        }

        return tempImage;

    }

    // Constructor
    public GridAdapter(Context c) {

        mContext = c;

    }

    public int getCount() {
        return champImage.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) {
            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;
        }

        imageView.setImageResource(champImage[position]);
        return imageView;
    }

    // Keep all Images in array

}

}

Answer 1

尝试下面的代码或使用getFragmentManager()或getParent();

public class ChampionInfo extends FragmentActivity {

GridView gridtable;

Context ctx;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_champion_info);
    ctx=ChampionInfo.this;//getFragmentManager() or getParent()
    gridtable = (GridView) findViewById(R.id.gridtable);        
    gridtable.setAdapter(new GridAdapter(ctx));

}

public class GridAdapter extends BaseAdapter {
    private Context mContext;

    String[] list = getResources().getStringArray(R.array.championlist);

    int[] champImage = getImage();

    public int[] getImage() {

        int[] tempImage = new int[list.length];

        for (int i = 0; i < list.length; i++) {
            tempImage[i] = getResources().getIdentifier(list[i],
                    "drawable", getPackageName());
        }

        return tempImage;

    }

    // Constructor
    public GridAdapter(Context c) {

        mContext = c;

    }

    public int getCount() {
        return champImage.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) {
            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;
        }

        imageView.setImageResource(champImage[position]);
        return imageView;
    }

    // Keep all Images in array

}
}