不顯示列表視圖的自定義適配器

Question

我的自定義適配器不會打印出ListView。在我的代碼中，我從URL中獲取JSON輸入並解析它以顯示在我的自定義ListView中。

MainActivity.java：

public class MainActivity extends AppCompatActivity { 

    private ProgressDialog pDialog; 

    ArrayList<String> workList; 

    String title; 
    String imagepathview; 
    String description; 

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

     DisplayImageOptions defaultOptions = new DisplayImageOptions.Builder() 
       .cacheOnDisc(true).cacheInMemory(true) 
       .imageScaleType(ImageScaleType.EXACTLY) 
       .displayer(new FadeInBitmapDisplayer(300)).build(); 

     ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(
       getApplicationContext()) 
       .defaultDisplayImageOptions(defaultOptions) 
       .memoryCache(new WeakMemoryCache()) 
       .discCacheSize(100 * 1024 * 1024).build(); 

     ImageLoader.getInstance().init(config); 
     workList = new ArrayList<>(); 

     new GetWork().execute(); 
    } 

    private class GetWork extends AsyncTask<Void, Void, Void> { 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      pDialog = new ProgressDialog(MainActivity.this); 
      pDialog.setMessage("Loading Work..."); 
      pDialog.setCancelable(false); 
      pDialog.show(); 

     } 

     @RequiresApi(api = Build.VERSION_CODES.KITKAT) 
     @Override 
     protected Void doInBackground(Void... arg0) { 

      Context context; 

      // URL to get JSON data 
      String url = "http:xyz.json"; 


      FirstAccessInDay f = new FirstAccessInDay(); //Makes HTTPHandler call and returns the JSON. 
      String jsonStr = f.firstaccess(url); 

      workList = null; 
      JSONArray a; 
      String key; 

      if (jsonStr != null) { 
       try { 

        JSONObject jsonObj = new JSONObject(jsonStr); 
        workList = new ArrayList<>(); 

        Iterator iterator = jsonObj.keys(); 
        while (iterator.hasNext()) { 
         key = (String) iterator.next(); 

         // Getting JSON Array node 
         a = jsonObj.getJSONArray(key); 

         int j = 0; 

           JSONObject c = a.getJSONObject(j); 
           JSONObject d = a.getJSONObject(j + 1); 
           JSONObject e = a.getJSONObject(j + 2); 

           title = c.getString("title"); 
           imagepathview = d.getString("image"); 
           description = e.getString("description"); 


           workList.add(title); 
           workList.add(imagepathview); 
           workList.add(description); 

         } 
       } catch (JSONException e) { 
        e.printStackTrace(); 
       } 
      } 
      return null; 
     } 

     @Override 
     protected void onPostExecute(Void result) { 
      super.onPostExecute(result); 
      // Dismiss the progress dialog 
      if (pDialog.isShowing()) 
       pDialog.dismiss(); 
      /** 
      * Updating parsed JSON data into ListView 
      * */ 
      ListView lv = (ListView) findViewById(R.id.list); 
      ArrayAdapter adapter = new CustomListAdapter(MainActivity.this,R.layout.mylist,workList); 
      lv.setAdapter(adapter); 
     } 
    } 
} 

CustomListAdapter.java：

class CustomListAdapter extends ArrayAdapter<String> implements Adapter { 

    private final Activity context; 
    private ArrayList worklist; 

    static class ViewHolder{ 
     TextView txtTitle; 
     ImageView imageView; 
     TextView extratxt; 
    } 

    CustomListAdapter(Activity context, int listViewId, ArrayList worklist) { 
     super(context, listViewId); 
     // TODO Auto-generated constructor stub 

     this.context = context; 
     this.worklist = worklist; 

    } 

    @NonNull 
    public View getView(int position, View view, @NonNull ViewGroup parent) { 
     ViewHolder holder; 
     View rowView= view; 
     ImageLoader imageLoader = null; 


      if (rowView == null) { 
       LayoutInflater inflater = (LayoutInflater) context.getLayoutInflater(); 
       rowView = inflater.inflate(R.layout.mylist, parent, false); 

       holder = new ViewHolder(); 

       imageLoader = ImageLoader.getInstance(); 

       holder.txtTitle = (TextView) rowView.findViewById(R.id.title); 
       holder.imageView = (ImageView) rowView.findViewById(R.id.image); 
       holder.extratxt = (TextView) rowView.findViewById(R.id.description); 
       rowView.setTag(holder); 
      } 
     else { 
       holder = (ViewHolder) rowView.getTag(); 
      } 
       String title = (String)worklist.get(position); 
       holder.txtTitle.setText(title); 

       String imagepathview = (String)worklist.get(position); 
       imageLoader.displayImage(imagepathview, holder.imageView); 

       String description = (String) worklist.get(position); 
       holder.extratxt.setText(description); 

     return rowView; 
    } 
} 

這是我的logcat：

Process pipe failed 

                      [ 03-01 14:36:02.192 4772: 4806 D/   ] 
                      HostConnection::get() New Host Connection established 0x7f04c6b3e020, tid 4806 
03-01 14:36:02.203 4772-4806/com.example.customlistview I/OpenGLRenderer: Initialized EGL, version 1.4 
03-01 14:36:02.265 4772-4806/com.example.customlistview E/EGL_emulation: tid 4806: eglSurfaceAttrib(1165): error 0x3009 (EGL_BAD_MATCH) 
03-01 14:36:02.266 4772-4806/com.example.customlistview W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0x7f04bde0b2c0, error=EGL_BAD_MATCH 
03-01 14:36:02.347 4772-4806/com.example.customlistview E/EGL_emulation: tid 4806: eglSurfaceAttrib(1165): error 0x3009 (EGL_BAD_MATCH) 
03-01 14:36:02.347 4772-4806/com.example.customlistview W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0x7f04bde0b300, error=EGL_BAD_MATCH 
03-01 14:36:03.937 4772-4806/com.example.customlistview E/Surface: getSlotFromBufferLocked: unknown buffer: 0x7f04bf6d0a80 
03-01 14:36:03.959 4772-4772/com.example.customlistview D/AndroidRuntime: Shutting down VM 
03-01 14:36:03.968 4772-4772/com.example.customlistview E/AndroidRuntime: FATAL EXCEPTION: main 
                      Process: com.example.customlistview, PID: 4772 
                      java.lang.ClassCastException: java.lang.String cannot be cast to com.example.customlistview.ModelClass 
                       at com.example.customlistview.CustomListAdapter.getView(CustomListAdapter.java:73) 
                       at android.widget.AbsListView.obtainView(AbsListView.java:2346) 
                       at android.widget.ListView.measureHeightOfChildren(ListView.java:1280) 
                       at android.widget.ListView.onMeasure(ListView.java:1188) 
                       at android.view.View.measure(View.java:18788) 
                       at android.widget.RelativeLayout.measureChild(RelativeLayout.java:676) 
                       at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:479) 
                       at android.view.View.measure(View.java:18788) 
                       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
                       at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
                       at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139) 
                       at android.view.View.measure(View.java:18788) 
                       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
                       at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:393) 
                       at android.view.View.measure(View.java:18788) 
                       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
                       at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
                       at android.view.View.measure(View.java:18788) 
                       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
                       at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465) 
                       at android.widget.LinearLayout.measureVertical(LinearLayout.java:748) 
                       at android.widget.LinearLayout.onMeasure(LinearLayout.java:630) 
                       at android.view.View.measure(View.java:18788) 
                       at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951) 
                       at android.widget.FrameLayout.onMeasure(FrameLayout.java:194) 
                       at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643) 
                       at android.view.View.measure(View.java:18788) 
                       at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100) 
                       at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216) 
                       at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452) 
                       at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107) 
                       at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013) 
                       at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858) 
                       at android.view.Choreographer.doCallbacks(Choreographer.java:670) 
                       at android.view.Choreographer.doFrame(Choreographer.java:606) 
                       at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844) 
                       at android.os.Handler.handleCallback(Handler.java:739) 
                       at android.os.Handler.dispatchMessage(Handler.java:95) 
                       at android.os.Looper.loop(Looper.java:148) 
                       at android.app.ActivityThread.main(ActivityThread.java:5417) 
                       at java.lang.reflect.Method.invoke(Native Method) 
                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
03-01 14:36:06.429 4772-4772/com.example.customlistview I/Process: Sending signal. PID: 4772 SIG: 9 

Answer 1

起初設定getCount將（）方法

@Override 
    public int getCount() { 
     return worklist.size(); 
    } 

確保您的workList.size（）返回0或。

創建一個模型類

public class ModelClass implements Serializable{ 

    public String title, description,image; 

    public ModelClass() 
    { 

    } 
    public ModelClass(String title, String description,String image) { 
     this.title = title; 
     this.description = description; 
     this.image = image; 


    } 


    public String get_title() { 
     return this.title; 
    } 
    public String get_description() { 
     return this.description; 
    } 
    public String get_image() { 
     return this.image; 
    } 

    public void set_title(String title){this.id = title;} 
    public void set_description(String description){this.description = description;} 
    public void set_image(String image){this.image = image;} 

} 

聲明

ArrayList<ModelClass> al_Test  = new ArrayList<ModelClass>(); 

然後

ModelClass test_Obj = new ModelClass(title,imagepathview,description); 
al_Test.add(test_Obj); 

轉到適配器

String title =worklist.get(position).get_title(); 
      holder.txtTitle.setText(title);