如何在从JSON中获取数据后在另一个Fragment Activity中添加Imageview

Question

我有一个使用TabHost运行的android应用程序。一旦在MainActivity中获得JSON数据，我想在另一个片段活动中更新并添加图像视图。但当我打电话给shp时。在MainActivity类中添加Images（），应用程序崩溃。请帮助~~

public class MainActivity extends FragmentActivity implements OnTabChangeListener, OnPageChangeListener {
    private TabsPagerAdapter mAdapter;
    private ViewPager mViewPager;
    private TabHost mTabHost;
    private String server_url = "http://comicking.blob.core.windows.net/xml/testing.json";
    private JSONHandler obj;
    private Handler mHandler = new Handler();
    ArrayList<Book> bookList;
    BookAdapter bookadapter;

    @TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH) 
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bookList = new ArrayList<Book>();
        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        InitialiseTabHost();
        mAdapter = new TabsPagerAdapter(getSupportFragmentManager());             
        mViewPager.setAdapter(mAdapter);
        mViewPager.setOnPageChangeListener(MainActivity.this);
        new JSONAsyncTask().execute(server_url);
        bookadapter = new BookAdapter(getApplicationContext(), R.layout.row, bookList);
        Shop shop = new Shop();
        shop.AddImages(bookList);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
     // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle presses on the action bar items
        switch (item.getItemId()) {
            case R.id.Refresh:
                //openSearch();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
    // Method to add a TabHost
    private static void AddTab(MainActivity activity, TabHost tabHost, TabHost.TabSpec tabSpec) {
        tabSpec.setContent(new MyTabFactory(activity));
        tabHost.addTab(tabSpec);
    }
    // Manages the Tab changes, synchronizing it with Pages
    public void onTabChanged(String tag) {
        int pos = this.mTabHost.getCurrentTab();
        this.mViewPager.setCurrentItem(pos);
    }
    @Override
    public void onPageScrollStateChanged(int arg0) {
    }
    // Manages the Page changes, synchronizing it with Tabs
    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        int pos = this.mViewPager.getCurrentItem();
        this.mTabHost.setCurrentTab(pos);
    }
    @Override
    public void onPageSelected(int arg0) {
    }
    private void InitialiseTabHost() {
        mTabHost = (TabHost) findViewById(android.R.id.tabhost);
        mTabHost.setup();
        MainActivity.AddTab(this, this.mTabHost, this.mTabHost.newTabSpec("Home").setIndicator("Home"));
        MainActivity.AddTab(this, this.mTabHost, this.mTabHost.newTabSpec("Shop").setIndicator("Shop"));
        MainActivity.AddTab(this, this.mTabHost, this.mTabHost.newTabSpec("Collection").setIndicator("Collection"));
        MainActivity.AddTab(this, this.mTabHost, this.mTabHost.newTabSpec("Help").setIndicator("Help"));
        mTabHost.setOnTabChangedListener(this);
    }

异步任务类

class JSONAsyncTask extends AsyncTask<String, Void, Boolean> {
        ProgressDialog dialog;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            dialog = new ProgressDialog(MainActivity.this);
            dialog.setMessage("Loading, please wait");
            dialog.setTitle("Connecting server");
            dialog.show();
            dialog.setCancelable(false);
        }
        @Override
        protected Boolean doInBackground(String... urls) {
            try {
                //------------------>>
                HttpGet httppost = new HttpGet(urls[0]);
                HttpClient httpclient = new DefaultHttpClient();
                HttpResponse response = httpclient.execute(httppost);
                // StatusLine stat = response.getStatusLine();
                int status = response.getStatusLine().getStatusCode();
                if (status == 200) {
                    HttpEntity entity = response.getEntity();
                    String data = EntityUtils.toString(entity);

                    JSONObject jsono = new JSONObject(data);
                    JSONArray jarray = jsono.getJSONArray("book");
                    for (int i = 0; i < jarray.length(); i++) {
                        JSONObject object = jarray.getJSONObject(i);
                        Book book = new Book();
                        book.setName(object.getString("name"));
                        book.setImage(object.getString("img"));
                        bookList.add(book);
                    }
                    return true;
                }
                //------------------>>
            } catch (ParseException e1) {
                e1.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }
            return false;
        }
        protected void onPostExecute(Boolean result) {
            dialog.cancel();
            //bookadapter.notifyDataSetChanged();
            if(result == false)
                Toast.makeText(getApplicationContext(), "Unable to fetch data from server", Toast.LENGTH_LONG).show();
        }
    }

}

碎片类

public class Shop extends Fragment {
    public Map<String,Book> shoplist = new HashMap<String,Book>();
    private View rootView;
    private LinearLayout shopLL;
    private Context c;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.shop, container, false);
        shopLL = (LinearLayout) rootView.findViewById(R.id.shopLinearLayout);
        return rootView;
    }
    public void AddImages(ArrayList<Book> booklist){
        c = getActivity().getApplicationContext();
        for(int i = 0; i < booklist.size(); i++){
            ImageView img= new ImageView(c);
            shopLL.addView(img);
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<TabHost
android:id="@android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout
    android:layout_width="match_parent"
    android:id="@+id/linearLayout1"
    android:layout_height="match_parent">
    <TabWidget
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@android:id/tabs"
        android:layout_alignParentBottom="true">
    </TabWidget>
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@android:id/tabcontent">
    </FrameLayout>
    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_above="@android:id/tabs"
        android:layout_gravity="bottom" />
</RelativeLayout>
</TabHost>

Shop.xml

<RelativeLayout       xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<HorizontalScrollView
    android:id="@+id/horizontalScrollView1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true" >
    <LinearLayout
         android:id="@+id/shopLinearLayout"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:orientation="horizontal" >
            <ImageView
                android:id="@+id/item1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                 android:src="@drawable/ic_launcher" />
    </LinearLayout>
</HorizontalScrollView>

</RelativeLayout>

Answer 1

你能发布你的布局xml吗？假设您在布局文件中定义了"Shop"片段，您可以通过id获得对该片段的引用。然后，您可以使用返回的列表调用Shop片段类上的方法。

Answer 2

Asynctask是你使用的后端服务，你可以返回一个对象而不是布尔

JSONAsyncTask的修改：-

//**** e.g.
class JSONAsyncTask extends AsyncTask<String, Void, JSONObject> {
    // define a caller
    Shop caller;
    //create a Constructor for caller;
    public JSONAsyncTask (Shop caller) {
        // TODO Auto-generated constructor stub
         this.caller = caller;
    }
    ///&& method doInBackground
    @Override
    protected JSONObject doInBackground(String... urls) {
          .....

         //custom your returning jsonObject 
         return jsonobject;
    }
    ////&& return jsonobject back to ur fragment class here by pass in caller
    protected void onPostExecute(JSONObject jsonObject) {
        caller.onBackgroundTaskCompleted(jsonObject);
    }
}

在将MainActivity类方法转换为Shop fragment类的过程中，获取ur json对象：-

    @Override
    public void onResume() {
           new JSONAsyncTask().execute(server_url);
    }

//your returning result
public void onBackgroundTaskCompleted(JSONObject result) {
        Log.i("TAG", result:"+result);
        if(result!=null){
            //process your result to get the booklist here
            Booklist booklist;

           addimage(booklist);

         }
}

Gd Luck:）