java - 无法实例化 Activity

Question

我创建另一个类 Voice 然后使用抽象类 voice，出错了

更新1

public class MainActivity extends ActionBarActivity {
    Voice v;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        v.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    }

05-27 11:42:30.432  17775-17775/com.example.mtartin.myapplication1 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mtartin.myapplication1/com.example.mtartin.myapplication1.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
            at android.app.ActivityThread.access$700(ActivityThread.java:140)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4921)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.example.mtartin.myapplication1.MainActivity.onCreate(MainActivity.java:24)
            at android.app.Activity.performCreate(Activity.java:5206)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
            at android.app.ActivityThread.access$700(ActivityThread.java:140)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4921)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
            at dalvik.system.NativeStart.main(Native Method)

我关注这个 https://www.youtube.com/watch?v=XGvUCx9FBS4

它可以使项目成功当我在三星手机调试中运行应用程序时，它有错误，

只有这个没问题公共(public)类 MainActivity 扩展了 ActionBarActivity

但它要求使用abstract类否则无法创建项目

05-27 10:14:41.338  12876-12876/com.example.mtartin.myapplication1 E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.mtartin.myapplication1/com.example.mtartin.myapplication1.MainActivity}: java.lang.InstantiationException: can't instantiate class com.example.mtartin.myapplication1.MainActivity
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2034)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
            at android.app.ActivityThread.access$700(ActivityThread.java:140)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4921)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.InstantiationException: can't instantiate class com.example.mtartin.myapplication1.MainActivity
            at java.lang.Class.newInstanceImpl(Native Method)
            at java.lang.Class.newInstance(Class.java:1319)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1068)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2025)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
            at android.app.ActivityThread.access$700(ActivityThread.java:140)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4921)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
            at dalvik.system.NativeStart.main(Native Method)

package com.example.mtartin.myapplication1;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.speech.RecognizerIntent;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;

import java.util.ArrayList;

/**
 * Created by MTartin on 27/5/2015.
 */
public abstract class Voice extends Activity implements View.OnClickListener {
    ListView lv;
    static final int check = 1111;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView)findViewById(R.id.lvVoiceReturn);
        Button b = (Button)findViewById(R.id.bVoice);
        b.setOnClickListener(this);
    }



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    //@Override
    public void OnClick(View v){
        Intent i = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
        i.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
        i.putExtra(RecognizerIntent.EXTRA_PROMPT, "speak up son!");
        startActivityForResult(i, check);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data){
        if(requestCode == check && resultCode == RESULT_OK){
            ArrayList<String> results = data.getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);
            lv.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, results));
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}


<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Speak"
        android:id="@+id/bVoice" />
    <ListView android:layout_height="fill_parent" android:id="@+id/lvVoiceReturn"
        android:layout_width="match_parent" android:layout_weight="1.44"></ListView>
</LinearLayout>

Answer 1

删除此 public abstract class MainActivity 并使用前一个类public class MainActivity 并创建一个不同的类 public abstract class MyDiffclass 并使用里面的代码