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Android：运行时从SQLite数据库读取数据

androidruntime-errorandroid-sqlitesqlite
3

我已经创建了一个数据库用于我的Android应用程序。我想要做的事情很简单，只是从我的数据库中读取数据并在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，每次我在模拟器中运行应用程序时，它都会崩溃。但是，如果我使用 tv.setText(cur.getString(0)); 而不是 tv.setText(cur.getString(1)); ，则可以使TextView显示'en_US'（我实际上不想显示这个，可能是由于地区设置），并且在按下任意一个按钮时应用程序会崩溃。
以下是LogCat中显示的错误信息：
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

以下是我的xml，这并不重要，无论如何，

<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（文本）字段的值为'en_US'，另一个表是'tix'，主字段为'_id'，其他字段为'jokes'。就是这样。
有人能指出问题在哪里吗？我该如何纠正它？我肯定需要帮助，因为这是我第一次尝试使用数据库 :/
请考虑使用 SQLiteAssetHelper 来处理预打包数据库的设置：https://github.com/jgilfelt/android-sqlite-asset-helper - CommonsWare
我不是很清楚，但从我读到的来看，它基本上做了相同的事情。至于尝试，我刚刚尝试了，没有帮助，仍然得到完全相同的错误信息。谢谢。 - iMan
请帮忙解决这个问题：http://stackoverflow.com/questions/20728808/android-reading-stored-sqlite-database - gandharv09
1个回答
3

仅仅把光标放入TextView中是不起作用的。您需要先获取内容。

您可以在您的DB类中尝试像这样：

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;
}

在你的TextView中：

tv.setText(dbh.data());

或者类似这样的东西

不是最好的方法，但应该能够工作

谢谢，但不幸的是，它不起作用。我认为可能与列或行索引有关？我的数据库中有2个表，android_metadata和tix，但如何从数据库中选择tix表呢？我已经搜索了很多，没有找到帮助我的解释。显然我一点都不知道。 - iMan
您可以在查询中选择数据库。DB_NAME 是您的表名。 - mike.b93
谢谢，现在我可以部分地访问我的数据库了。假设我的数据库是这样的：|--------------------------|| _id | jokes | |--------------------------| | 1 | jokeA | | 2 | jokeB | |--------------------------|现在当我使用 getString(0) 时，输出为 "1"，而使用 getString(1) 时则输出 "jokeA"，那么我该如何获取 "jokeB" 呢？任何其他整数值都会导致应用程序崩溃！ - iMan
我刚刚意识到你必须指定其他语句。我今天稍后会添加另一个答案。我现在很忙:)坚持:)与此同时，您可以阅读查询的文档:) - mike.b93
1
好的，只需将查询更改为所需操作即可。http://goo.gl/0jg3k 设置从活动传递到查询中的变量，以便您可以查询数据库中的几乎任何数据。 - mike.b93
谢谢你容忍我，稍后我会告诉你这是否有效，希望有效。 :) - iMan
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