Question

所以我在这里有这些代码，它运行时没有崩溃。但是，当我通过＆＃34;这个＆＃34;在gridadapter中，mContext为null。我试图通过getApplicationContext（）但仍然无法使getImage方法正常运行，因为getResources.getIdentifier行没有返回任何内容，因为Context为null。我很感激，如果有人可以教我如何发生这种情况，我该如何解决它。感谢。

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

尝试以下代码或使用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

}
}

Answer 2

private Context context;
   private ProgressDialog progressDialog;

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

    context = this;
 }

Answer 3

问题的根源在于您尝试使用

内联初始化成员变量

int[] champImage = getImage();

执行之前将mContext设置为有效值的构造函数。但是，mContext调用null getImage()的事实应该是无关紧要的，因为您实际上从未在该方法中使用mContext。

总体问题是你需要注意执行的顺序。

Answer 4

尝试使用此代码

 Context mContext;

GridView gridtable;

 @Override
public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_champion_info);
   mContext=this;
   gridtable = (GridView) findViewById(R.id.gridtable);        
   gridtable.setAdapter(new GridAdapter(mContext));

}

Edit1：尝试使用getActivity（）来获取上下文

Answer 5

我认为mContext不为null，但getResources（）方法返回null。

如下所示更改您的代码，如果不起作用，请重试。粘贴 Logcat ，我们可以调试代码。

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

和

public int[] getImage() {

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

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

    return tempImage;

}

Android活动上下文为空

5 个答案: