所以我在我的Android应用程序中创建了一个数据库。我想做的很简单，只需从我的数据库中读取并在TextView中显示数据，这里是DataBaseHelper类
package com.tix.activity;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper{
private static String DB_PATH = "/data/data/com.tix.activity/databases/";
private static String DB_NAME = "tix";
private SQLiteDatabase myDatabase;
private final Context myContext;
public DatabaseHelper (Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
}
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
}else{
this.getReadableDatabase();
try{
copyDataBase();
}catch (IOException e) {
throw new Error("Error copying Database");
}
}
}
private boolean checkDataBase() {
// TODO Auto-generated method stub
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
private void copyDataBase() throws IOException{
InputStream myInput = myContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer))>0){
myOutput.write(buffer,0,length);
}
myOutput.flush();
myOutput.close();
myInput.close();
}
public void openDataBase() throws SQLException{
String myPath = DB_PATH + DB_NAME;
myDatabase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@Override
public synchronized void close(){
if(myDatabase != null)
myDatabase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db){
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public Cursor data(){
Cursor c;
c = myDatabase.query(DB_NAME,null,null,null,null,null,null);
return c;
}
}
这是我的MainActivity类
package com.tix.activity;
import java.io.IOException;
import android.os.Bundle;
import android.app.Activity;
import android.database.Cursor;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends Activity {
Cursor cur;
TextView tv;
Button next, prev;
DatabaseHelper dbh;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv = (TextView)findViewById(R.id.tv);
next = (Button)findViewById(R.id.nbtn);
prev = (Button)findViewById(R.id.pbtn);
dbh = new DatabaseHelper(this);
try {
dbh.createDataBase();
} catch (IOException e2) {
e2.printStackTrace();
}
dbh.openDataBase();
cur = dbh.data();
cur.moveToFirst();
tv.setText(cur.getString(1));
next.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(cur.isLast())
{
cur.moveToFirst();
tv.setText(""+cur.getString(1));
}
else
{
cur.moveToNext();
tv.setText(""+cur.getString(1));
}
}
});
prev.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(cur.isFirst()){
cur.moveToLast();
tv.setText(""+cur.getString(1));
}
else
{
cur.moveToPrevious();
tv.setText(""+cur.getString(1));
}
}
});
}
}
但是，每当我在模拟器中运行应用程序时，它就会崩溃。但是，如果我投入 tv.setText（cur.getString（0））; 代替 tv.setText（cur.getString（1））;
然后我得到textview以显示'en_US'（我不想显示它，可能是来自语言环境）并且在按下任一按钮时应用程序崩溃。
这是我在LogCat上的错误，
07-03 16:37:45.120: E/CursorWindow(1912): Failed to read row 0, column 1 from a CursorWindow which has 1 rows, 1 columns.
07-03 16:37:45.160: D/AndroidRuntime(1912): Shutting down VM
07-03 16:37:45.160: W/dalvikvm(1912): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
07-03 16:37:45.180: E/AndroidRuntime(1912): FATAL EXCEPTION: main
07-03 16:37:45.180: E/AndroidRuntime(1912): java.lang.IllegalStateException: Couldn't read row 0, col 1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.database.CursorWindow.nativeGetString(Native Method)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.database.CursorWindow.getString(CursorWindow.java:434)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
07-03 16:37:45.180: E/AndroidRuntime(1912): at com.tix.activity.MainActivity$2.onClick(MainActivity.java:65)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.view.View.performClick(View.java:4202)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.view.View$PerformClick.run(View.java:17340)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.os.Handler.handleCallback(Handler.java:725)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.os.Handler.dispatchMessage(Handler.java:92)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.os.Looper.loop(Looper.java:137)
07-03 16:37:45.180: E/AndroidRuntime(1912): at android.app.ActivityThread.main(ActivityThread.java:5039)
07-03 16:37:45.180: E/AndroidRuntime(1912): at java.lang.reflect.Method.invokeNative(Native Method)
07-03 16:37:45.180: E/AndroidRuntime(1912): at java.lang.reflect.Method.invoke(Method.java:511)
07-03 16:37:45.180: E/AndroidRuntime(1912): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-03 16:37:45.180: E/AndroidRuntime(1912): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-03 16:37:45.180: E/AndroidRuntime(1912): at dalvik.system.NativeStart.main(Native Method)
07-03 16:39:01.480: I/Process(1912): Sending signal. PID: 1912 SIG: 9
07-03 16:39:30.201: W/Trace(1966): Unexpected value from nativeGetEnabledTags: 0
07-03 16:39:30.201: W/Trace(1966): Unexpected value from nativeGetEnabledTags: 0
07-03 16:39:30.631: W/Trace(1966): Unexpected value from nativeGetEnabledTags: 0
07-03 16:39:30.631: W/Trace(1966): Unexpected value from nativeGetEnabledTags: 0
07-03 16:39:31.522: E/CursorWindow(1966): Failed to read row 0, column 1 from a CursorWindow which has 1 rows, 1 columns.
07-03 16:39:31.531: D/AndroidRuntime(1966): Shutting down VM
07-03 16:39:31.531: W/dalvikvm(1966): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
07-03 16:39:31.582: E/AndroidRuntime(1966): FATAL EXCEPTION: main
07-03 16:39:31.582: E/AndroidRuntime(1966): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tix.activity/com.tix.activity.MainActivity}: java.lang.IllegalStateException: Couldn't read row 0, col 1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.ActivityThread.access$600(ActivityThread.java:141)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.os.Handler.dispatchMessage(Handler.java:99)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.os.Looper.loop(Looper.java:137)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.ActivityThread.main(ActivityThread.java:5039)
07-03 16:39:31.582: E/AndroidRuntime(1966): at java.lang.reflect.Method.invokeNative(Native Method)
07-03 16:39:31.582: E/AndroidRuntime(1966): at java.lang.reflect.Method.invoke(Method.java:511)
07-03 16:39:31.582: E/AndroidRuntime(1966): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-03 16:39:31.582: E/AndroidRuntime(1966): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-03 16:39:31.582: E/AndroidRuntime(1966): at dalvik.system.NativeStart.main(Native Method)
07-03 16:39:31.582: E/AndroidRuntime(1966): Caused by: java.lang.IllegalStateException: Couldn't read row 0, col 1 from CursorWindow. Make sure the Cursor is initialized correctly before accessing data from it.
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.database.CursorWindow.nativeGetString(Native Method)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.database.CursorWindow.getString(CursorWindow.java:434)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
07-03 16:39:31.582: E/AndroidRuntime(1966): at com.tix.activity.MainActivity.onCreate(MainActivity.java:38)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.Activity.performCreate(Activity.java:5104)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
07-03 16:39:31.582: E/AndroidRuntime(1966): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
07-03 16:39:31.582: E/AndroidRuntime(1966): ... 11 more
我的xml如下，无论如何，这无关紧要，
<RelativeLayout 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"
tools:context=".MainActivity" >
<Button
android:id="@+id/pbtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="33dp"
android:layout_marginTop="48dp"
android:text="Back" />
<Button
android:id="@+id/nbtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/pbtn"
android:layout_alignBottom="@+id/pbtn"
android:layout_alignParentRight="true"
android:layout_marginRight="25dp"
android:text="Next" />
<TextView
android:id="@+id/tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/pbtn"
android:layout_centerHorizontal="true"
android:layout_marginTop="141dp"
android:text="Large Text"
android:textAppearance="?android:attr/textAppearanceLarge" />
</RelativeLayout>
我使用SQLite数据库浏览器创建了数据库，但它包含一个名为android_metadata的表，其中locale（text）字段的值为'en_US'，另一个表是'tix'，主字段为'_id'，另一个字段为作为'笑话'。就是这样。
有谁可以指出出了什么问题？我该如何纠正呢？我肯定需要帮助，因为这是我在数据库中的第一次拍摄：/
答案 0 :(得分：3)
将光标放入TextView不起作用。您需要先获取内容。
你想在你的数据库类中尝试这样：
public String data(){
Cursor c;
String result;
c = myDatabase.query(DB_NAME,null,null,null,null,null,null);
try {
if (c.moveToFirst()) {
result = cursor.getString(0);
}
result = c.getString(0);
} finally {
c.close();
}
return result;
}
并在TextView中：
tv.setText(dbh.data());
或类似的东西
不是最好的方式，但应该工作