Question

我已经按照本教程this tutorial设置了我的DatBas和主要活动以适应教程。我收到了一个错误：

E / AndroidRuntime（281）：java.lang.RuntimeException：无法启动活动ComponentInfo {com.xxx.xxx/com.xxx.xxx.Tamar_appActivity}：java.lang.NullPointerException

Tamar_appActivity代码为：

        DatBas db = new DatBas(this);
    TamarDatabaseCursor c = db.getActress();

    if (c.moveToFirst())
        DisplayRadioButton(c);
    else
        Toast.makeText(this, "No title found", Toast.LENGTH_LONG).show();
    db.close();

}

public void DisplayRadioButton(Cursor c) {
    for (int i = 1; i < (c.getColumnCount()); i++) {
        RadioGroup radiogroup = (RadioGroup)      findViewById(R.id.NameSelectGroup);
        RadioButton rdbtn = new RadioButton(this);
        rdbtn.setId(i);
        rdbtn.setText(c.getString(i));
        radiogroup.addView(rdbtn);
    }

}

数据库代码是：

public class DatBas {


public static final String KEY_ROW_ID = "_id";
public static final String KEY_IMAGE_PATH = "uri";
public static final String KEY_NAME = "name";
public static final String KEY_GENDER = "gender";
public static final String KEY_BORN_DATE_YEAR = "age_year";
public static final String KEY_BORN_DATE_MONTH = "age_month";
public static final String KEY_BORN_DATE_DAY = "age_day";

private static final String DATABASE_NAME = "TamatDB";
private static final String DATABASE_TABLE_SETTINGS = "settings";

private static final int DATABASE_VERSION = 20;

private TamarDatabase thdb;
private static Context tcontext;
private SQLiteDatabase tdb;

private static class TamarDatabase extends SQLiteOpenHelper {

    public TamarDatabase(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String ctSettings = "CREATE TABLE " + DATABASE_TABLE_SETTINGS
                + " ( " + KEY_ROW_ID
                + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                + KEY_IMAGE_PATH + " TEXT NOT NULL, " + KEY_NAME
                + " TEXT NOT NULL, " + KEY_GENDER + " TEXT NOT NULL, "
                + KEY_BORN_DATE_YEAR + " TEXT NOT NULL, "
                + KEY_BABY_DATE_MONTH + " TEXT NOT NULL, "
                + KEY_BABY_DATE_DAY + " TEXT NOT NULL);";
        db.execSQL(ctSettings);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE_SETTINGS);
        onCreate(db);
    }
}

public DatBas(Context c) {
    tcontext = c;
}

public DatBas open() throws SQLiteException {
    thdb = new TamarDatabase(tcontext);
    tdb = thdb.getWritableDatabase();
    return this;
}

public void close() {
    thdb.close();
}

public long createEntrySettings(String bbdy, String bbdm, String bbdd,
        String pt, String bg, String bfName) {
    ContentValues cv2 = new ContentValues();
    cv2.put(KEY_IMAGE_PATH, pt);
    cv2.put(KEY_NAME, bfName);
    cv2.put(KEY_GENDER, bg);
    cv2.put(KEY_BORN_DATE_YEAR, bbdy);
    cv2.put(KEY_BORN_DATE_MONTH, bbdm);
    cv2.put(KEY_BORN_DATE_DAY, bbdd);

    return tdb.insert(DATABASE_TABLE_SETTINGS, null, cv2);
}

public Cursor getDataSettings() {
    String[] columns = new String[] { KEY_ROW_ID, KEY_IMAGE_PATH,
            KEY_NAME, KEY_GENDER, KEY_BORN_DATE_YEAR,
            KEY_BORN_DATE_MONTH, KEY_BORN_DATE_DAY };
    Cursor c = tdb.query(DATABASE_TABLE_SETTINGS, columns, null, null,
            null, null, null);
    String results = "";

    int iRawId = c.getColumnIndex(KEY_ROW_ID);
    int iBIPath = c.getColumnIndex(KEY_IMAGE_PATH);
    int iBName = c.getColumnIndex(KEY_NAME);
    int iGender = c.getColumnIndex(KEY_GENDER);
    int iBBDateYear = c.getColumnIndex(KEY_BORN_DATE_YEAR);
    int iBBDateMonth = c.getColumnIndex(KEY_BORN_DATE_MONTH);
    int iBBDateDay = c.getColumnIndex(KEY_BORN_DATE_DAY);

    for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
        results = results + " the kind is " + " " + c.getString(iRawId)
                + " the kind is " + " " + c.getString(iBIPath)
                + " the kind is " + " " + c.getString(iBName)
                + " the kind is " + " " + c.getString(iGender)
                + " the kind is " + " " + c.getString(iBBDateYear)
                + " the kind is " + " " + c.getString(iBBDateMonth)
                + " the kind is " + " " + c.getString(iBBDateDay) + "\n";
    }
    return c;
}

public String getDataSettingsBabyName() {
    String[] columns = new String[] { KEY_ROW_ID, KEY_NAME};
    Cursor c = tdb.query(DATABASE_TABLE_SETTINGS, columns, null, null,
            null, null, null);
    String results = "";

    int iRawId = c.getColumnIndex(KEY_ROW_ID);
    int iBName = c.getColumnIndex(KEY_NAME);

    for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
        String[] resultsS = new String[]{c.getString(iRawId), c.getString(iBName)       
        };
    }
    return results;
}




public static class TamarDatabaseCursor extends SQLiteCursor{

    /** The query for this cursor */
    private static final String QUERY = 
        "SELECT _id, uri, baby_name, gender, age_year, age_month, age_day" +
        " FROM settings";

    /** Cursor constructor */
    private TamarDatabaseCursor(SQLiteDatabase db, SQLiteCursorDriver driver,
            String editTable, SQLiteQuery query) {
        super(db, driver, editTable, query);
    }
    /** Private factory class necessary for rawQueryWithFactory() call */

    private static class Factory implements SQLiteDatabase.CursorFactory{
        public Cursor newCursor(SQLiteDatabase db,
                SQLiteCursorDriver driver, String editTable,
                SQLiteQuery query) {
            return new TamarDatabaseCursor(db, driver, editTable, query);
        }
    }
    /* Accessor functions get one per database column */

    public int getActressId(){return getInt(getColumnIndexOrThrow("actress.actressId"));}

}



public TamarDatabaseCursor getActress()
{
SQLiteDatabase d = getReadableDatabase();
TamarDatabaseCursor c = (TamarDatabaseCursor)d.rawQueryWithFactory
        (new TamarDatabaseCursor.Factory(), TamarDatabaseCursor.QUERY, null, null);
c.moveToFirst();
return c;
}



private SQLiteDatabase getReadableDatabase() {
    // TODO Auto-generated method stub
    return null;
}

public DatBas delete() {
    tdb.delete(DATABASE_TABLE, null, null);
    tdb.delete(DATABASE_TABLE_SETTINGS, null, null);
    return null;
}
}

主XML是：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#3691c9"
android:orientation="vertical" >

<RadioGroup
    android:id="@+id/sideGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:weightSum="100" >

    <RadioButton
        android:id="@+id/rbtnLeft"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="50"
        android:text="xxx" />

    <RadioButton
        android:id="@+id/rbtnRight"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="50"
        android:text="xxx" />
</RadioGroup>

<RadioGroup
    android:id="@+id/kindGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:weightSum="100" >

    <RadioButton
        android:id="@+id/rbtnN"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="50"
        android:text="xxx" />

    <RadioButton
        android:id="@+id/rbtnP"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="50"
        android:text="xxx" />
</RadioGroup>

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:text="TextView"
    android:textColor="#363636"
    android:textSize="25dp" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="TextView"
    android:textColor="#363636"
    android:textSize="40dp"
    android:textStyle="bold" />

<Button
    android:id="@+id/button2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Start" />

<Button
    android:id="@+id/button3"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Pause" />

<Button
    android:id="@+id/Button4"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Resume" />

<Button
    android:id="@+id/button1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Stop" />

<RadioGroup
    android:id="@+id/NameSelectGroup"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" >

    <RadioButton
        android:id="@+id/bNameSelect"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:text="RadioButton" />
</RadioGroup>

<ImageButton
    android:id="@+id/imageButton1"
    android:layout_width="38dp"
    android:layout_height="37dp"
    android:src="@android:drawable/ic_menu_manage" />

<ImageView
    android:id="@+id/imageView1"
    android:layout_width="160dp"
    android:layout_height="160dp"
    android:layout_gravity="center"
    android:src="@android:drawable/gallery_thumb" />

</LinearLayout>

Answer 1

我会猜测findViewById(R.id.babyNameSelectGroup);返回null，当你尝试radiogroup.addView(rdbtn);时，你会得到NPE。

在尝试访问布局中包含的视图之前，您是否已完成setContentView(R.layout.yourmainlayout);？

修改

您正在寻找babyNameSelectGroup，这在您的布局中似乎不存在（从而为您提供NPE）。也许它应该是NameSelectGroup？

Answer 2

我必须设置getReadableDatabase()方法：

    public SQLiteDatabase getReadableDatabase() throws SQLiteException {
    thdb = new TamarDatabase(tcontext);
    tdb = thdb.getReadableDatabase();
    return tdb;
}

Android从数据库表中填充单选按钮

2 个答案: