我想要查看自制数据库的应用程序没有运行“查看”按钮。
这是我的logcat，有可能我没有声明我的Manifest吗？
logcat的：
12-14 06:56:56.316: E/AndroidRuntime(1144): FATAL EXCEPTION: main
12-14 06:56:56.316: E/AndroidRuntime(1144): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jacob.eindproject/com.jacob.eindproject.SQLView}: java.lang.NullPointerException
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.ActivityThread.access$600(ActivityThread.java:141)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.os.Handler.dispatchMessage(Handler.java:99)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.os.Looper.loop(Looper.java:137)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.ActivityThread.main(ActivityThread.java:5103)
12-14 06:56:56.316: E/AndroidRuntime(1144): at java.lang.reflect.Method.invokeNative(Native Method)
12-14 06:56:56.316: E/AndroidRuntime(1144): at java.lang.reflect.Method.invoke(Method.java:525)
12-14 06:56:56.316: E/AndroidRuntime(1144): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
12-14 06:56:56.316: E/AndroidRuntime(1144): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
12-14 06:56:56.316: E/AndroidRuntime(1144): at dalvik.system.NativeStart.main(Native Method)
12-14 06:56:56.316: E/AndroidRuntime(1144): Caused by: java.lang.NullPointerException
12-14 06:56:56.316: E/AndroidRuntime(1144): at com.jacob.eindproject.Database.<init>(Database.java:63)
12-14 06:56:56.316: E/AndroidRuntime(1144): at com.jacob.eindproject.SQLView.onCreate(SQLView.java:14)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.Activity.performCreate(Activity.java:5133)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
12-14 06:56:56.316: E/AndroidRuntime(1144): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
12-14 06:56:56.316: E/AndroidRuntime(1144): ... 11 more
这是我的机器人清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.jacob.eindproject"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.jacob.eindproject.Menu"
android:label="@string/app_name" >
</activity>
<activity
android:name="com.jacob.eindproject.Inleiding"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.jacob.eindproject.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.jacob.eindproject.Ondergewicht"
android:label="@string/app_name" >
</activity>
<activity
android:name="com.jacob.eindproject.Gezond_gewicht"
android:label="@string/app_name" >
</activity>
<activity
android:name="com.jacob.eindproject.Overgewicht"
android:label="@string/app_name" >
</activity>
<activity
android:name="com.jacob.eindproject.Database"
android:label="@string/app_name" >
</activity>
<activity
android:name="com.jacob.eindproject.SQLite"
android:label="@string/app_name" >
</activity>
<activity
android:name="com.jacob.eindproject.SQLView"
android:label="@string/app_name" >
</activity>
</application>
</manifest>
这是我的观点类：
package com.jacob.eindproject;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class SQLView extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.sqlview);
TextView tv = (TextView) findViewById(R.id.tvSQLinfo);
Database info = new Database(this);
info.open();
String data = info.getData();
info.close();
tv.setText(data);
}
}
这是我的view.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TableLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:id="@+id/tableLayout1">
<TableRow>
<TextView android:text="@string/Names" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1"/>
<TextView android:text="@string/Hotness" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_weight="1" />
</TableRow>
</TableLayout>
<TextView android:id="@+id/tvSQLinfo" android:layout_width="fill_parent" android:layout_height="fill_parent" android:text="@string/info"/>
</LinearLayout>
这是我的数据库类：
package com.jacob.eindproject;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import java.sql.*;
public class Database {
public static final String KEY_ROWID = "_id";
public static final String KEY_NAME = "persons_name";
public static final String KEY_HOTNESS = "persons_hotness";
private static final String DATABASE_NAME = "HotOrNotdb";
private static final String DATABASE_TABLE = "peopleTable";
private static final int DATABASE_VERSION = 1;
private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private static class DbHelper extends SQLiteOpenHelper{
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
KEY_NAME + " TEXT NOT NULL, " +
KEY_HOTNESS + " TEXT NOT NULL);"
);
}
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public Database(Context c){
ourContext = c;
}
public Database open() throws SQLException{
ourHelper = new DbHelper(ourContext);
ourDatabase = ourHelper.getWritableDatabase();
return this;
}
public void close() {
} {
ourHelper.close();
}
public void createEntry(String name, String hotness) {
ContentValues cv = new ContentValues();
cv.put(KEY_NAME, name);
cv.put(KEY_HOTNESS, hotness);
ourDatabase.insert(DATABASE_TABLE, null, cv);
}
public String getData() {
// TODO Auto-generated method stub
String[] columns = new String[]{ KEY_ROWID, KEY_NAME, KEY_HOTNESS};
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
String result = "";
int iRow = c.getColumnIndex(KEY_ROWID);
int iName = c.getColumnIndex(DATABASE_NAME);
int iHotness = c.getColumnIndex(KEY_HOTNESS);
for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
result = result + c.getString(iRow) + " " + c.getString(iName) + " " + c.getString(iHotness) + "\n";
}
return null;
}
}
有人可以帮助我吗？太棒了！
雅各
答案 0 :(得分：0)
删除此
<activity
android:name="com.jacob.eindproject.Database"
android:label="@string/app_name" >
</activity>
Database不是activity。