0

私の AndroidMenifest.xml を見てください

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

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" >
    </uses-permission>

    <application
        android:allowBackup="true"
        android:debuggable="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity      android:name="com.myapp.activities.exercisesetsactivity.ExercisesetsActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <activity
            android:name="com.myapp.activities.mainactivity.MainActivity"
            android:label="@string/app_name" >
            <!--intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter-->
        </activity>

        <service
            android:name="com.myapp.services.guideservice.GuideService"
            android:exported="false" >
        </service>
    </application>
    </manifest>

最初は、MainActivity がデフォルトのアクティビティでした。後で、ExercisesetsActivity に変更しようとしました。それが、logcat で以下のエラーが発生し始めた場所です。

 > 
    01-22 22:09:51.831: E/AndroidRuntime(22676): FATAL EXCEPTION: main
        01-22 22:09:51.831: E/AndroidRuntime(22676): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.myapp/com.myapp.activities.exercisesetsactivity.ExercisesetsActivity}: java.lang.NullPointerException
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.app.ActivityThread.access$600(ActivityThread.java:130)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.os.Handler.dispatchMessage(Handler.java:99)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.os.Looper.loop(Looper.java:137)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.app.ActivityThread.main(ActivityThread.java:4745)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at java.lang.reflect.Method.invokeNative(Native Method)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at java.lang.reflect.Method.invoke(Method.java:511)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at dalvik.system.NativeStart.main(Native Method)
        01-22 22:09:51.831: E/AndroidRuntime(22676): Caused by: java.lang.NullPointerException
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:101)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at com.myapp.activities.exercisesetsactivity.ExercisesetsActivity.<init>(ExercisesetsActivity.java:24)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at java.lang.Class.newInstanceImpl(Native Method)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at java.lang.Class.newInstance(Class.java:1319)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
        01-22 22:09:51.831: E/AndroidRuntime(22676):    ... 11 more

MainActivity に変更すると、正常に動作します。ただし、ExercisesetsActivity を最初に表示する必要があります。

package com.myapp.activities.exercisesetsactivity;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;

import com.myapp.R;
import com.myapp.activities.mainactivity.MainActivity;
import com.myapp.businessclasses.Exercisesetlist;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class ExercisesetsActivity extends Activity {
**private Exercisesetlist myExerciseSetList = new Exercisesetlist(this.getApplicationContext());**

private class currentListAdapter extends ArrayAdapter<String> {

    public currentListAdapter() {
        super(ExercisesetsActivity.this, R.layout.activity_exercisesetlist,
                ExercisesetsActivity.this.myExerciseSetList.setNames);
        // TODO Auto-generated constructor stub
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        LayoutInflater inflater = getLayoutInflater();

        View row = inflater.inflate(R.layout.activity_exercisesetlist, parent,
                false);
        TextView label = (TextView) row.findViewById(R.id.tvItems);

        String strContent = ExercisesetsActivity.this.myExerciseSetList.setNames
                .get(position);
        label.setText(strContent);
        label.setTag(position);
        label.setOnClickListener(exerciseClickListner);

        return row;
    }

}

private android.view.View.OnClickListener exerciseClickListner = new android.view.View.OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        int pos = (Integer) v.getTag();

        Intent intent = new Intent(ExercisesetsActivity.this.getApplicationContext(),
                MainActivity.class);
        intent.putExtra(ExercisesetsActivity.this.getResources().getString(R.string.EXERCISESETID),
                ExercisesetsActivity.this.myExerciseSetList.setIDs.get(pos));
        startActivity(intent);
    }
};

// This is temporary
public void copyDBifnotexists() {
    String DATABASE_PATH = Environment.getExternalStorageDirectory()
            .getPath() + "/myapp/data/";
    String DATABSE_NAME = "db.db";

    File folders = new File(DATABASE_PATH);
    File file = new File(folders, DATABSE_NAME);
    if (!file.exists()) {
        folders.mkdirs();

        try {
            InputStream inputStream = this.getResources().openRawResource(
                    R.raw.db);
            FileOutputStream fileOutputStream = new FileOutputStream(file);

            byte buf[] = new byte[1024];
            int len;
            while ((len = inputStream.read(buf)) > 0) {
                fileOutputStream.write(buf, 0, len);
            }

            fileOutputStream.close();
            inputStream.close();
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }
}


/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // TODO Auto-generated method stub
    setContentView(R.layout.activity_exercisesetlist);

    // This is temporary
    copyDBifnotexists();

    ListView lv = (ListView) findViewById(R.id.lvExerciselist);
    lv.setAdapter(new currentListAdapter());
}
}
4

4 に答える 4

1

以下のように、アクティビティのメソッドでのインスタンスを初期化しますExercisesetlist myExerciseSetList。onCreate()

 public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
         // TODO Auto-generated method stub
         setContentView(R.layout.activity_exercisesetlist);
         myExerciseSetList = new Exercisesetlist(this.getApplicationContext());
      }
于 2013-01-23T05:04:28.717 に答える
1

私はこれに答えようと試みます。私が想定しているのExercisesetlistは、ヘルパークラス（セッター/ゲッター）です。

これを変える：

private Exercisesetlist myExerciseSetList = new Exercisesetlist(this.getApplicationContext());

これに：

public class ExercisesetsActivity extends Activity {
    private Exercisesetlist myExerciseSetList;
    ....
    ....
}

と：

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // TODO Auto-generated method stub
    setContentView(R.layout.activity_exercisesetlist);

    // This is temporary
    copyDBifnotexists();

    // INSTANTIATE THE Exercisesetlist INSTANCE
    myExerciseSetList = new Exercisesetlist(ExercisesetsActivity.this);

    ListView lv = (ListView) findViewById(R.id.lvExerciselist);
    lv.setAdapter(new currentListAdapter());
}
于 2013-01-23T05:04:41.540 に答える
1 
private Exercisesetlist myExerciseSetList = new Exercisesetlist(this.getApplicationContext());

よくわかりませんが、OnCreate() メソッドを呼び出さないと、そのアクティビティのコンテキストを取得できない可能性があります。したがって、以下のように OnCreate() メソッド内でこれを初期化して、何が起こるかを確認してください。

private Exercisesetlist myExerciseSetList;
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // TODO Auto-generated method stub
    setContentView(R.layout.activity_exercisesetlist);

    myExerciseSetList = new Exercisesetlist(this.getApplicationContext());

}

それがあなたを助けることを願っています。

于 2013-01-23T05:02:00.800 に答える
0

マニフェストファイルで、アクティビティタグでandroid：nameを次のように指定しました

        android:name="com.myapp.activities.exercisesetsactivity.ExercisesetsActivity"

com.myappを削除し、次のように指定します

      android:name=".activities.exercisesetsactivity.ExercisesetsActivity"

そうすれば、エラーは発生しません。

于 2013-01-23T06:31:06.197 に答える