android - 从适配器启动 Activity 不适用于 SwipeListView 库

Question

我正在使用 SwipeListView库，尝试在我的适配器中启动 Activity 时出现错误。

public class ProductAdapter extends ArrayAdapter<Product> {

private Context context;

public ProductAdapter(Context context, int textViewResourceId, List<Product> objects) {
    super(context, textViewResourceId, objects);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    ViewHolder viewHolder;

    final Product product = getItem(position);

    if (convertView == null) {
        viewHolder = new ViewHolder();

        convertView = LayoutInflater.from(getContext()).inflate(R.layout.cproduct_list_item, null);

        viewHolder.nom = (TextView) convertView.findViewById(R.id.name);
        viewHolder.commerce = (TextView) convertView.findViewById(R.id.commerce);
        viewHolder.prix = (TextView) convertView.findViewById(R.id.price);
        viewHolder.bAction1 = (Button) convertView.findViewById(R.id.example_row_b_action_1);
        viewHolder.bAction2 = (Button) convertView.findViewById(R.id.example_row_b_action_2);
        viewHolder.bAction3 = (Button) convertView.findViewById(R.id.example_row_b_action_3);

        convertView.setTag(viewHolder);

    } 
    else {
        viewHolder = (ViewHolder) convertView.getTag();
    }

    viewHolder.nom.setText(product.getName());
    viewHolder.commerce.setText(product.getCommerce());
    viewHolder.prix.setText(String.format("%s F", product.getPrice()));

    viewHolder.bAction1.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(context, MainActivity.class);
            context.startActivity(intent);
        }
    });

    return convertView;
}

private class ViewHolder {
    TextView nom;
    TextView commerce;
    TextView prix;
    Button bAction1;
    Button bAction2;
    Button bAction3;
}
}

当我点击按钮时，我得到这个错误:“应用程序意外停止”。但是当我使用 Toast 时，它工作正常。我认为开始 Activity 有些不一致。

日志:

04-16 18:42:29.531: E/AndroidRuntime(29813): FATAL EXCEPTION: main 04-16 18:42:29.531: E/AndroidRuntime(29813): java.lang.NullPointerException 04-16 18:42:29.531: E/AndroidRuntime(29813): at com.tomsyweb.suna.ProductAdapter$2.onClick(ProductAdapter.java:71) 04-16 18:42:29.531: E/AndroidRuntime(29813): at android.view.View.performClick(View.java:2485) 04-16 18:42:29.531: E/AndroidRuntime(29813): at android.view.View$PerformClick.run(View.java:9080) 04-16 18:42:29.531: E/AndroidRuntime(29813): at android.os.Handler.handleCallback(Handler.java:587) 04-16 18:42:29.531: E/AndroidRuntime(29813): at android.os.Handler.dispatchMessage(Handler.java:92) 04-16 18:42:29.531: E/AndroidRuntime(29813): at android.os.Looper.loop(Looper.java:130) 04-16 18:42:29.531: E/AndroidRuntime(29813): at android.app.ActivityThread.main(ActivityThread.java:3687) 04-16 18:42:29.531: E/AndroidRuntime(29813): at java.lang.reflect.Method.invokeNative(Native Method) 04-16 18:42:29.531: E/AndroidRuntime(29813): at java.lang.reflect.Method.invoke(Method.java:507) 04-16 18:42:29.531: E/AndroidRuntime(29813): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867) 04-16 18:42:29.531: E/AndroidRuntime(29813): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625) 04-16 18:42:29.531: E/AndroidRuntime(29813): at dalvik.system.NativeStart.main(Native Method)

Answer 1

context 在您的案例中是 ProductAdapter 的一个字段，您没有使用任何值对其进行初始化，因此它是 null。请改用 getContext() 或使用 this.context = context 初始化 context 字段。