java.lang.InstantiationException: невозможно создать экземпляр класса?

Question

Я пытаюсь сделать Android приложения с автоматической генерацией форм http://labs.makemachine.net/2010/04/android-form-generator/

Я читал много о теме «InstantiationException», но никто не решить мою проблему.

Вот моя активность

package com.example.makemachine; 

import java.io.IOException; 
import java.io.InputStream; 
import java.util.ArrayList; 
import java.util.Collections; 
import java.util.Comparator; 
import java.util.HashMap; 
import java.util.Map; 

import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import android.app.Activity; 
import android.content.Context; 
import android.util.Log; 
import android.view.View; 
import android.widget.LinearLayout; 
import android.widget.ScrollView; 
import android.widget.LinearLayout.LayoutParams; 

/** 
* FormActivity allows you to create dynamic form layouts based upon a json schema file. 
* This class should be sub-classed. 
* 
* @author Jeremy Brown 
*/ 
public abstract class FormActivity extends Activity 
{ 
    public static String SCHEMA_KEY_TYPE  = "type"; 
    public static String SCHEMA_KEY_BOOL  = "boolean"; 
    public static String SCHEMA_KEY_INT   = "integer"; 
    public static String SCHEMA_KEY_STRING  = "string"; 
    public static String SCHEMA_KEY_PRIORITY = "priority"; 
    public static String SCHEMA_KEY_TOGGLES  = "toggles"; 
    public static String SCHEMA_KEY_DEFAULT  = "default"; 
    public static String SCHEMA_KEY_MODIFIERS = "modifiers"; 
    public static String SCHEMA_KEY_OPTIONS  = "options"; 
    public static String SCHEMA_KEY_META  = "meta"; 
    public static String SCHEMA_KEY_HINT  = "hint"; 

    public static final LayoutParams defaultLayoutParams = new LinearLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT); 

    // -- data 
    protected Map<String, FormWidget> _map; 
    protected ArrayList<FormWidget> _widgets; 

    // -- widgets 
    protected LinearLayout _container; 
    protected LinearLayout _layout; 
    protected ScrollView _viewport; 

    // ----------------------------------------------- 
    // 
    // parse data and build view 
    // 
    // ----------------------------------------------- 

    /** 
    * parses a supplied schema of raw json data and creates widgets 
    * @param data - the raw json data as a String 
    */ 
    public FormActivity(){ 
     super(); 
    } 
    public void generateForm(String data) 
    { 
     _widgets = new ArrayList<FormWidget>(); 
     _map = new HashMap<String, FormWidget>(); 

     try 
     { 
      String name; 
      FormWidget widget; 
      JSONObject property; 
      JSONObject schema = new JSONObject(data); 
      JSONArray names = schema.names(); 

      for(int i= 0; i < names.length(); i++) 
      { 
       name = names.getString(i); 

       if(name.equals(SCHEMA_KEY_META) ) continue; 

       property = schema.getJSONObject(name);  

       boolean toggles = hasToggles(property); 
       String defaultValue = getDefault(property); 
       int priority = property.getInt(FormActivity.SCHEMA_KEY_PRIORITY); 

       widget = getWidget(name, property); 
       if(widget == null) continue; 

       widget.setPriority(priority); 
       widget.setValue(defaultValue); 

       if(toggles){ 
        widget.setToggles(processToggles(property)); 
        widget.setToggleHandler(new FormActivity.FormWidgetToggleHandler()); 
       } 

       if(property.has(FormActivity.SCHEMA_KEY_HINT)) widget.setHint(property.getString(FormActivity.SCHEMA_KEY_HINT)); 

       _widgets.add(widget); 
       _map.put(name, widget); 
      } 
     } catch(JSONException e) { 
      Log.i("MakeMachine", e.getMessage()); 
     } 

     // -- sort widgets on priority 
     Collections.sort(_widgets, new PriorityComparison()); 

     // -- create the layout 
     _container = new LinearLayout(this); 
     _container.setOrientation(LinearLayout.VERTICAL); 
     _container.setLayoutParams(FormActivity.defaultLayoutParams); 

     _viewport = new ScrollView(this); 
     _viewport.setLayoutParams(FormActivity.defaultLayoutParams); 

     _layout = new LinearLayout(this); 
     _layout.setOrientation(LinearLayout.VERTICAL); 
     _layout.setLayoutParams(FormActivity.defaultLayoutParams); 

     initToggles(); 

     for(int i = 0; i < _widgets.size(); i++) { 
      _layout.addView((View) _widgets.get(i).getView()); 
     } 

     _viewport.addView(_layout); 
     _container.addView(_viewport); 

     setContentView(_container); 
    } 

    // ----------------------------------------------- 
    // 
    // populate and save 
    // 
    // ----------------------------------------------- 

    /** 
    * this method fills the form with existing data 
    * get the json string stored in the record we are editing 
    * create a json object (if this fails then we know there is now existing record) 
    * create a list of property names from the json object 
    * loop through the map returned by the Form class that maps widgets to property names 
    * if the map contains the property name as a key that means there is a widget to populate w/ a value 
    */ 
    protected void populate(String jsonString) 
    { 
     try 
     { 
      String prop; 
      FormWidget widget; 
      JSONObject data = new JSONObject(jsonString); 
      JSONArray properties = data.names(); 

      for(int i = 0; i < properties.length(); i ++) 
      { 
       prop = properties.getString(i); 
       if(_map.containsKey(prop)) { 
        widget = _map.get(prop); 
        widget.setValue(data.getString(prop)); 
       } 
      } 
     } catch (JSONException e) { 

     } 
    } 

    /** 
    * this method preps the data and saves it 
    * if there is a problem w/ creating the json string, the method fails 
    * loop through each widget and set a property on a json object to the value of the widget's getValue() method 
    */ 
    protected JSONObject save() 
    { 
     FormWidget widget; 
     JSONObject data = new JSONObject(); 

     boolean success = true; 

     try{ 
      for(int i = 0; i < _widgets.size(); i++) 
      { 
       widget = _widgets.get(i); 
       data.put(widget.getPropertyName(), widget.getValue()); 
      } 
     } catch(JSONException e) 
     { 
      success = false; 
      Log.i("MakeMachine", "Save error - " + e.getMessage()); 
      return null; 
     } 

     if(success) { 
      Log.i("MakeMachine", "Save success " + data.toString()); 
      return data; 
     } 
     return null; 
    } 

    // ----------------------------------------------- 
    // 
    // toggles 
    // 
    // ----------------------------------------------- 

    /** 
    * creates the map a map of values for visibility and references to the widgets the value affects 
    */ 
    protected HashMap<String, ArrayList<String>> processToggles(JSONObject property) 
    { 
     try{ 
      ArrayList<String> toggled; 
      HashMap<String, ArrayList<String>> toggleMap = new HashMap<String, ArrayList<String>>(); 

      JSONObject toggleList = property.getJSONObject(FormActivity.SCHEMA_KEY_TOGGLES); 
      JSONArray toggleNames = toggleList.names(); 

      for(int j = 0; j < toggleNames.length(); j++) 
      { 
       String toggleName = toggleNames.getString(j); 
       JSONArray toggleValues = toggleList.getJSONArray(toggleName); 
       toggled = new ArrayList<String>(); 
       toggleMap.put(toggleName, toggled); 
       for(int k = 0; k < toggleValues.length(); k++) { 
        toggled.add(toggleValues.getString(k)); 
       } 
      } 

      return toggleMap; 

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

    /** 
    * returns a boolean indicating that the supplied json object contains a property for toggles 
    */ 
    protected boolean hasToggles(JSONObject obj){ 
     try{ 
      obj.getJSONObject(FormActivity.SCHEMA_KEY_TOGGLES); 
      return true; 
     } catch (JSONException e){ 
      return false; 
     } 
    } 

    /** 
    * initializes the visibility of widgets that are togglable 
    */ 
    protected void initToggles() 
    { 
     int i; 
     FormWidget widget; 

     for(i = 0; i < _widgets.size(); i++) { 
      widget = _widgets.get(i); 
      updateToggles(widget); 
     } 
    } 

    /** 
    * updates any widgets that need to be toggled on or off 
    * @param widget 
    */ 
    protected void updateToggles(FormWidget widget) 
    { 
     int i; 
     String name; 
     ArrayList<String> toggles; 
     ArrayList<FormWidget> ignore = new ArrayList<FormWidget>(); 

     toggles = widget.getToggledOn(); 
     for(i = 0; i < toggles.size(); i++) 
     { 
      name = toggles.get(i); 
      if(_map.get(name) != null) 
      { 
       FormWidget toggle = _map.get(name); 
       ignore.add(toggle); 
       toggle.setVisibility(View.VISIBLE); 
      } 
     } 

     toggles = widget.getToggledOff(); 
     for(i = 0; i < toggles.size(); i++) 
     { 
      name = toggles.get(i); 
      if(_map.get(name) != null) 
      { 
       FormWidget toggle = _map.get(name); 
       if(ignore.contains(toggle)) continue; 
       toggle.setVisibility(View.GONE); 
      } 
     } 
    } 

    /** 
    * simple callbacks for widgets to use when their values have changed 
    */ 
    class FormWidgetToggleHandler 
    { 
     public void toggle(FormWidget widget) { 
      updateToggles(widget); 
     } 
    } 

    // ----------------------------------------------- 
    // 
    // utils 
    // 
    // ----------------------------------------------- 

    protected String getDefault(JSONObject obj){ 
     try{ 
      return obj.getString(FormActivity.SCHEMA_KEY_DEFAULT); 
     } catch (JSONException e){ 
      return null; 
     } 
    } 

    /** 
    * helper class for sorting widgets based on priority 
    */ 
    class PriorityComparison implements Comparator<FormWidget> 
    { 
     public int compare(FormWidget item1, FormWidget item2) { 
      return item1.getPriority() > item2.getPriority() ? 1 : -1; 
     } 
    } 

    /** 
    * factory method for actually instantiating widgets 
    */ 
    protected FormWidget getWidget(String name, JSONObject property) 
    { 
     try 
     { 
      String type = property.getString(FormActivity.SCHEMA_KEY_TYPE); 

      if(type.equals(FormActivity.SCHEMA_KEY_STRING)){ 
       return new FormEditText(this, name ); 
      } 

      if(type.equals(FormActivity.SCHEMA_KEY_BOOL)){ 
       return new FormCheckBox(this, name); 
      } 

      if(type.equals( FormActivity.SCHEMA_KEY_INT)) 
      { 
       if(property.has(FormActivity.SCHEMA_KEY_OPTIONS)) 
       { 
        JSONObject options = property.getJSONObject(FormActivity.SCHEMA_KEY_OPTIONS); 
        return new FormSpinner( this, name, options); 
       }else{ 
        return new FormNumericEditText(this, name); 
       } 
      } 
     } catch(JSONException e) { 
      return null; 
     } 
     return null; 
    } 

    public static String parseFileToString(Context context, String filename) 
    { 
     try 
     { 
      InputStream stream = context.getAssets().open(filename); 
      int size = stream.available(); 

      byte[] bytes = new byte[size]; 
      stream.read(bytes); 
      stream.close(); 

      return new String(bytes); 

     } catch (IOException e) { 
      Log.i("MakeMachine", "IOException: " + e.getMessage()); 
     } 
     return null; 
    } 
} 

Manifest.xml

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.example.makemachine" 
    android:versionCode="1" 
    android:versionName="1.0" > 

    <uses-sdk 
     android:minSdkVersion="8" 
     android:targetSdkVersion="19" /> 

    <application 
     android:allowBackup="true" 
     android:icon="@drawable/ic_launcher" 
     android:label="@string/app_name" 
     android:theme="@style/AppTheme" > 
     <activity 
      android:name="com.example.makemachine.MainActivity" 
      android:label="@string/app_name" >  

     </activity> 
     <activity 
      android:name="com.example.makemachine.FormActivity" 
      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> 

Logcat Ошибка

12-22 10:41:01.791: E/AndroidRuntime(2953): FATAL EXCEPTION: main 
12-22 10:41:01.791: E/AndroidRuntime(2953): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.makemachine/com.example.makemachine.FormActivity}: java.lang.InstantiationException: can't instantiate class com.example.makemachine.FormActivity 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.os.Handler.dispatchMessage(Handler.java:99) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.os.Looper.loop(Looper.java:137) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at java.lang.reflect.Method.invokeNative(Native Method) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at java.lang.reflect.Method.invoke(Method.java:511) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at dalvik.system.NativeStart.main(Native Method) 
12-22 10:41:01.791: E/AndroidRuntime(2953): Caused by: java.lang.InstantiationException: can't instantiate class com.example.makemachine.FormActivity 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at java.lang.Class.newInstanceImpl(Native Method) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at java.lang.Class.newInstance(Class.java:1319) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.app.Instrumentation.newActivity(Instrumentation.java:1054) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097) 
12-22 10:41:01.791: E/AndroidRuntime(2953):  ... 11 more 

Что плохого в моем коде?

Answer 1

Ваш FormActivity is abstract и абстрактные классы не могут быть созданы.

Считая комментарии от сгенерированного кода, он говорит: «Этот класс должен быть подклассифицирован». Поэтому расширьте базу FormActivity и объявите неактивные производные классы активности в манифесте.