java - 无法实例化 Activity ComponentInfo 无法实例化类

Question

提前感谢所有看这个问题的人，尤其是那些试图回答的人!这个网站对我帮助很大!

我目前在我的 Android 4.2.2 应用程序中遇到以下错误。以下是日志:

09-09 01:14:27.008: D/dalvikvm(9008): newInstance failed: p0 i0 [0 a1
09-09 01:14:27.008: D/AndroidRuntime(9008): Shutting down VM
09-09 01:14:27.008: W/dalvikvm(9008): threadid=1: thread exiting with uncaught exception (group=0x41173ac8)
09-09 01:14:27.018: E/AndroidRuntime(9008): FATAL EXCEPTION: main
09-09 01:14:27.018: E/AndroidRuntime(9008): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.pocketbotanist/com.pocketbotanist.HomeScreen}: java.lang.InstantiationException: can't instantiate class com.pocketbotanist.HomeScreen
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2173)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2297)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.app.ActivityThread.access$700(ActivityThread.java:152)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1282)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.os.Looper.loop(Looper.java:137)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.app.ActivityThread.main(ActivityThread.java:5328)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at java.lang.reflect.Method.invokeNative(Native Method)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at java.lang.reflect.Method.invoke(Method.java:511)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at dalvik.system.NativeStart.main(Native Method)
09-09 01:14:27.018: E/AndroidRuntime(9008): Caused by: java.lang.InstantiationException: can't instantiate class com.pocketbotanist.HomeScreen
09-09 01:14:27.018: E/AndroidRuntime(9008):     at java.lang.Class.newInstanceImpl(Native Method)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at java.lang.Class.newInstance(Class.java:1319)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.app.Instrumentation.newActivity(Instrumentation.java:1071)
09-09 01:14:27.018: E/AndroidRuntime(9008):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2164)
09-09 01:14:27.018: E/AndroidRuntime(9008):     ... 11 more

我已经尝试清理一个项目，尝试修复我在其他地方看到的 Android 私有(private)库，并检查了我的包名称(除非我遗漏了什么，我可能是这样!)。这是 homescreen.java:

package com.pocketbotanist;

import java.io.File;

import android.app.ListActivity;
import android.app.LoaderManager;
import android.content.Intent;
import android.content.Loader;
import android.content.pm.ActivityInfo;
import android.content.res.Configuration;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.Spinner;

import com.pocketbotanist.contentprovider.MyEntryContentProvider;
import com.pocketbotanist.database.EntryTable;



public abstract class HomeScreen extends ListActivity implements LoaderManager.LoaderCallbacks<Cursor> {

    private static final int DELETE_ID = Menu.FIRST + 1;
    // private Cursor cursor;
    private SimpleCursorAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home_screen);
        this.getListView().setDividerHeight(2);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

        //Initial folder creation code
        File appDirectory = new File(Environment.getExternalStorageDirectory().toString()+"/Pocket Botanist/");
        if (!appDirectory.exists()){
            appDirectory.mkdir();
        }

        //Drop down list code
        Spinner spinner = (Spinner) findViewById(R.id.action_spinner);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.action_list, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);


        fillData();
        //View listItem=(View)((Menu) this.getListView()).getItem(0);
        registerForContextMenu(getListView());
        if (adapter.isEmpty())
            System.out.println("IT'S EMPTY");
        String[] projection = { EntryTable.COLUMN_CUSTOMID };
        long info =  adapter.getItemId(0);
        Uri uri = Uri.parse(MyEntryContentProvider.CONTENT_URI + "/"
                + info);
        Cursor cursor = getContentResolver().query(uri, projection, null, null, null);
        cursor.moveToFirst();
        System.out.println((cursor.getString(cursor
                    .getColumnIndexOrThrow(EntryTable.COLUMN_CUSTOMID))));
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    }


    @Override
    public boolean onContextItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case DELETE_ID:
            String[] projection = { EntryTable.COLUMN_PHOTOS };
            AdapterContextMenuInfo info = (AdapterContextMenuInfo) item
            .getMenuInfo();
            Uri uri = Uri.parse(MyEntryContentProvider.CONTENT_URI + "/"
                    + info.id);
            Cursor cursor = getContentResolver().query(uri, projection, null, null, null);
            cursor.moveToFirst();
            File temp = new File(cursor.getString(cursor
                    .getColumnIndexOrThrow(EntryTable.COLUMN_PHOTOS)));
            if(temp.exists()){
                File[] files = temp.listFiles();
                for(int i = 0; i < files.length; i++){
                    files[i].delete();
                }
                temp.delete();
            }
            getContentResolver().delete(uri, null, null);
            fillData();
            return true;
        }

        return super.onContextItemSelected(item);

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_home_screen, menu);
        //SearchView searchView = (SearchView) menu.findItem(R.id.menu_search).getActionView();
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
        case R.id.menu_settings:
            settCall();
            return true;
        case R.id.menu_map:
            map1_3();
            return true;
        case R.id.menu_edit:
            entryScreen("New Entry");
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

    public void entryScreen(String t){
        Intent intent = new Intent(this, EntryScreen.class);
        intent.putExtra("passer", t);
        startActivity(intent);
    }

    public void settCall(){
        Intent sett = new Intent(this,SettingsActivity.class);
        startActivity(sett);
    }

    public void map1_3(){

        Intent map13 = new Intent(this,Entrymap_1_3.class);
        startActivity(map13);
    }


    // Opens the second activity if an entry is clicked
    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);
        Intent i = new Intent(this, EntryScreen.class);
        Uri itemUri = Uri.parse(MyEntryContentProvider.CONTENT_URI + "/" + id);
        i.putExtra(MyEntryContentProvider.CONTENT_ITEM_TYPE, itemUri);

        startActivity(i);
    }

    //@Override
    //When we create the loader we're going to get the projection for the ID, customID, species name, and time columns
    //(insures that these exist within the database)
    //then we create our cursor loader which will be responsible for loading data from the database
    //using the projection and our content provider
    /* public Loader<Cursor> onCreateLoader(int arg0, Bundle arg1) {
        String[] projection = { EntryTable.COLUMN_ID, EntryTable.COLUMN_CUSTOMID, EntryTable.COLUMN_SPECIES, EntryTable.COLUMN_TIME, EntryTable.COLUMN_PHOTOS, EntryTable.COLUMN_PHOTO };
        CursorLoader cursor = new CursorLoader(this,
                MyEntryContentProvider.CONTENT_URI, projection, null, null, null);
        if (cursor != null) {
            ((Cursor) cursor).moveToFirst();
        }

        return cursor;
    } */

    private void fillData() {

        // Fields from the database (projection)
        String[] from = new String[] { EntryTable.COLUMN_CUSTOMID, EntryTable.COLUMN_SPECIES , EntryTable.COLUMN_TIME, EntryTable.COLUMN_PHOTO};
        // Fields on the UI to which we map
        int[] to = new int[] { R.id.customidlabel, R.id.namelabel, R.id.timelabel, R.id.imageView };

        getLoaderManager().initLoader(1, null, this);       //changed to 1
        adapter = new SimpleCursorAdapter(this, R.layout.list_row, null, from, to, 0);

        setListAdapter(adapter);
    }

    @Override
      public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        menu.add(0, DELETE_ID, 0, R.string.menu_delete);
      }


    @Override
    public void onLoadFinished(Loader<Cursor> arg0, Cursor data) {
        adapter.swapCursor(data);       
    }

    @Override
    public void onLoaderReset(Loader<Cursor> arg0) {
        adapter.swapCursor(null);
    }

}

我知道问题可能出在这里，所以这也是我的 AndroidManifest.xml 文件:

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

    <uses-sdk
        android:minSdkVersion="11"
        android:targetSdkVersion="18" />

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true"/>

    <permission
        android:name="com.pocketbotanist.permission.MAPS_RECEIVE"
        android:protectionLevel="signature"/>
<uses-permission android:name="com.pocketbotanist.permission.MAPS_RECEIVE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme"
        android:configChanges="keyboardHidden|orientation" >
        <activity
            android:name="com.pocketbotanist.HomeScreen"
            android:label="@string/main" >

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

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.pocketbotanist.EntryScreen"
            android:label="@string/title_activity_entry_screen"
            android:windowSoftInputMode="stateHidden" 
            >
        </activity>
        <activity
            android:name="com.pocketbotanist.SettingsActivity"
            android:label="@string/title_activity_settings" >
        </activity>
        <activity
            android:name="com.pocketbotanist.ManualLocationActivity"
            android:label="@string/title_activity_manual_location" >
        </activity>
        <activity
            android:name="com.pocketbotanist.Entrymap_1_3"
            android:label="@string/title_activity_entrymap_1_3" >
        </activity>
        <activity
            android:name="com.pocketbotanist.Location_2_3"
            android:label="@string/title_location_2_3" >
        </activity>
        <activity
            android:name="com.pocketbotanist.Mapfragmentpreview"
            android:configChanges="orientation|keyboardHidden|screenSize"
            android:label="@string/title_activity_mapfragmentpreview"
            android:theme="@style/FullscreenTheme" >
        </activity>

         <meta-data
            android:name="com.google.android.maps.v2.API_KEY"
            android:value="(removing key for security reasons)" />
         <uses-library  
       android:name="com.google.android.maps"  
       android:required="true" />

         <provider
      android:name="com.pocketbotanist.contentprovider.MyEntryContentProvider"
      android:authorities="com.pocketbotanist.contentprovider" 
      android:exported="false">
   </provider>
    </application>

</manifest>

有没有人有任何想法/建议？再次提前致谢!

Answer 1

根据定义，抽象类是不可实例化的。

改变

public abstract class HomeScreen extends ListActivity 

到

public class HomeScreen extends ListActivity