java - Json 和 ViewPager。 MainActivity 无法转换为 android.app.Activity

Question

我想要 json 和 viewpager。但我不能。错误 = MainActivity 无法转换为 android.app.Activity。我能做些什么 ？谢谢。

适配器

public class CustomAdapter extends PagerAdapter {

    Context context;
    String[] name;
    int[] image_url;
    LayoutInflater inflater;

    public CustomAdapter(Context context, String[] name, int[] image_url) {
        this.context = context;
        this.name = name;
        this.image_url = image_url;
    }

    @Override
    public int getCount() {
        return name.length;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == ((RelativeLayout) object);
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {

        // Declare Variables
        TextView txtname;
        ImageView img;

        inflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View itemView = inflater.inflate(R.layout.image_item, container,
                false);

        // Locate the TextViews in image_item.xml
        txtname = (TextView) itemView.findViewById(R.id.textView1);

        // Capture position and set to the TextViews
        txtname.setText(name[position]);

        // Locate the ImageView in image_item.xml
        img = (ImageView) itemView.findViewById(R.id.imageView);
        // Capture position and set to the ImageView
        img.setImageResource(image_url[position]);

        // Add image_item.xml to ViewPager
        ((ViewPager) container).addView(itemView);

        return itemView;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object)      {
        // Remove image_item.xml from ViewPager
        ((ViewPager) container).removeView((RelativeLayout) object);

    }

}

主要 Activity Json解析和viewpager

public class MainActivity extends Fragment {
    private static final String PROFILE_URL1 = "http://sunucupro.com/bt/1.txt";
    JSONObject event_slider;
    //private ProgressDialog pDialog;
    String category_id, id;
    String[] name;
    int[] image_url;
    ViewPager mViewPager;

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

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



        mViewPager = (ViewPager) rootView.findViewById(R.id.pager);

        new LoadSlider().execute();

        return rootView;
    }

    class LoadSlider extends AsyncTask<String, String, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        protected String doInBackground(String... args) {
            // Building Parameters
            String json = null;
            try {
                List<NameValuePair> params = new ArrayList<NameValuePair>();

                HttpClient httpclient = new DefaultHttpClient();
                HttpPost httppost = new HttpPost(PROFILE_URL1);
                httppost.setEntity(new UrlEncodedFormEntity(params));

                // Execute HTTP Post Request
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity resEntity = response.getEntity();
                json = EntityUtils.toString(resEntity);

                Log.i("All Slider: ", json.toString());
            } catch (Exception e) {
                e.printStackTrace();
            }

            return json;
        }

        @Override
        protected void onPostExecute(String json) {
            super.onPostExecute(json);

            //pDialog.dismiss();

            try {
                event_slider = new JSONObject(json);
                final ArrayList<HashMap<String, String>> arraylist = new ArrayList<HashMap<String, String>>();
                JSONArray user = event_slider.getJSONArray("data");

                for (int i = 0; i < user.length(); i++) {
                    JSONObject object = user.getJSONObject(i);
                    id = object.getString("id");
                    Log.i("id:", id);

                    HashMap<String, String> map = new HashMap<String, String>();
                    map.put("id", object.getString("id"));
                    map.put("name", object.getString("name"));
                    map.put("image_url", "http://www.iconsdb.com/icons/download/icon-sets/sketchy-pink/" + object.getString("images"));
                    arraylist.add(map);
                }

                name = new String[]{};

                image_url = new int[]{};

                PagerAdapter adapter = new CustomAdapter(getActivity(), name, image_url);
                mViewPager.setAdapter(adapter);

            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }
}

list 我将其更改为 android:name="com.sunucupro.deneme.MainActivity

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.sunucupro.deneme">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name="com.sunucupro.deneme.MainActivity"
            android:label="@string/app_name"

            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

如果您遵循 Android 命名约定，那么该错误就很有意义。

 public class MainActivity extends Fragment {

Fragment 不是 Activity，也不能这样转换。

改回来。

public class MainActivity extends AppCompatActivity {

并了解如何 create a Fragment correctly 。