java - 我应该如何替换可绘制对象？

Question

我有一个显示项目(可绘制+文本)的列表适配器。我在我的代码中添加了一个 RoundImage 类，以将可绘制对象替换为圆形的可绘制对象。代码如下:

@Override
public void onCreate(final Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);


    // cirlce avatars
    ImageView imageView1;
    RoundImage roundedImage;

    imageView1 = (ImageView)rootView.findViewById(R.id.avatar);
    Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.kamil);
    roundedImage = new RoundImage(bm);
    imageView1.setImageDrawable(roundedImage);
    //end circle avatars

}

接下来，在 onCreateView 中我使用了一个适配器:

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        rootView = inflater.inflate(R.layout.fragment_home, container, false);



        //button --------------------------
        add = (ImageButton) rootView.findViewById(R.id.add_button);
        add.setOnClickListener(this);
        //button --------------------------

        RowBean RowBean_data[] = new RowBean[]{
                new RowBean(R.drawable.kamilk, "Kamil "),
                new RowBean(R.drawable.bartlomiej, "Bartlomiej "),
                new RowBean(R.drawable.krzysztof, "Krzysztof ")
        };
        CustomAdapter adapter = new CustomAdapter(getActivity().getApplicationContext(), R.layout.list_style, RowBean_data);
        ListView lista = (ListView) rootView.findViewById(R.id.lista);
        lista.setAdapter(adapter);


        return rootView;

    }

但是我遇到了一个错误

java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.materialdesign/info.androidhive.materialdesign.activity.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference

所以我的问题是，我应该如何处理显示“roundedImage”的适配器？

我认为问题出在下面这行，我也尝试使用 getActivity().findViewbyId 但它也没有用。

imageView1 = (ImageView)rootView.findViewById(R.id.avatar);

Answer 1

info.androidhive.materialdesign.activity.HomeFragment.onCreate(HomeFragment.java:41)

这一行导致你的应用程序崩溃，我发现这一行包含以下指令

imageView1 = (ImageView)rootView.findViewById(R.id.avatar);

崩溃原因

应用程序正在崩溃，因为您的 rootView 在 onCreate 方法中为空，因为 onCreate() 在 onCreateView() 之前先执行请检查 fragment 的生命周期...!

解决方案

不要在onCreate方法中给出任何指令，使用下面的代码，

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        rootView = inflater.inflate(R.layout.fragment_home, container, false);

// cirlce avatars
    ImageView imageView1;
    RoundImage roundedImage;

    imageView1 = (ImageView)rootView.findViewById(R.id.avatar);
    Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.kamil);
    roundedImage = new RoundImage(bm);
    imageView1.setImageDrawable(roundedImage);
    //end circle avatars


        //button --------------------------
        add = (ImageButton) rootView.findViewById(R.id.add_button);
        add.setOnClickListener(this);
        //button --------------------------

        RowBean RowBean_data[] = new RowBean[]{
                new RowBean(R.drawable.kamilk, "Kamil "),
                new RowBean(R.drawable.bartlomiej, "Bartlomiej "),
                new RowBean(R.drawable.krzysztof, "Krzysztof ")
        };
        CustomAdapter adapter = new CustomAdapter(getActivity().getApplicationContext(), R.layout.list_style, RowBean_data);
        ListView lista = (ListView) rootView.findViewById(R.id.lista);
        lista.setAdapter(adapter);


        return rootView;

    }