Question

public String getDatatwo() {
    // TODO Auto-generated method stub
    String arg = "lol";
    String query = "select * from DATABASE_TABLE where title=\""+ arg +"\"";
    Cursor c = ourDatabase.rawQuery(query, null);
    int iName = c.getColumnIndex(KEY_NAME);
    String resultsearch = "";
    resultsearch = resultsearch + c.getString(iName);
    return resultsearch;
    }

基本上，它搜索DATABASE_TABLE搜索arg（“lol”）然后将其作为结果搜索返回，稍后显示。我试图让它在KEY_NAME行中搜索整个数据库并返回包含名称“lol”的所有数据。

如果可能的话，我也希望能够输入编辑arg的TextEdit，因为类扩展，我想我无法操纵arg。如果有人愿意提供帮助，我可以发送所有代码，如果有人可以看一下。

但是我收到了错误。

02-18 12:16:02.201: D/gralloc_goldfish(645): Emulator without GPU emulation detected.
02-18 12:16:24.111: E/SQLiteLog(645): (1) no such table: DATABASE_TABLE
02-18 12:16:24.111: D/AndroidRuntime(645): Shutting down VM
02-18 12:16:24.111: W/dalvikvm(645): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
02-18 12:16:24.151: E/AndroidRuntime(645): FATAL EXCEPTION: main
02-18 12:16:24.151: E/AndroidRuntime(645): java.lang.RuntimeException: Unable to start     activity ComponentInfo{com.example.sql/com.example.sql.SQLView}:   android.database.sqlite.SQLiteException: no such table: DATABASE_TABLE (code 1): , while   compiling: select * from DATABASE_TABLE where title="lol"
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
02-18 12:16:24.151: E/AndroidRuntime(645):  at  android.os.Handler.dispatchMessage(Handler.java:99)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.os.Looper.loop(Looper.java:137)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.ActivityThread.main(ActivityThread.java:4745)
02-18 12:16:24.151: E/AndroidRuntime(645):  at java.lang.reflect.Method.invokeNative(Native Method)
02-18 12:16:24.151: E/AndroidRuntime(645):  at java.lang.reflect.Method.invoke(Method.java:511)
02-18 12:16:24.151: E/AndroidRuntime(645):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-18 12:16:24.151: E/AndroidRuntime(645):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-18 12:16:24.151: E/AndroidRuntime(645):  at dalvik.system.NativeStart.main(Native Method)
02-18 12:16:24.151: E/AndroidRuntime(645): Caused by: android.database.sqlite.SQLiteException: no such table: DATABASE_TABLE (code 1): , while compiling: select * from DATABASE_TABLE where title="lol"
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
02-18 12:16:24.151: E/AndroidRuntime(645):  at   android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)
02-18 12:16:24.151: E/AndroidRuntime(645):  at  com.example.sql.DbMain.getDatatwo(DbMain.java:94)
02-18 12:16:24.151: E/AndroidRuntime(645):  at com.example.sql.SQLView.onCreate(SQLView.java:19)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.Activity.performCreate(Activity.java:5008)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
02-18 12:16:24.151: E/AndroidRuntime(645):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
02-18 12:16:24.151: E/AndroidRuntime(645):  ... 11 more
02-18 12:16:24.381: D/dalvikvm(645): GC_CONCURRENT freed 196K, 9% free 7469K/8199K, paused 19ms+33ms, total 192ms
02-18 12:16:26.741: I/Process(645): Sending signal. PID: 645 SIG: 9

修改了代码，仍然是错误。

    public String getDatatwo() {
    // TODO Auto-generated method stub
    String arg = "lol";
    Cursor c = ourDatabase.rawQuery("select * from " + DATABASE_TABLE + " where title=?"+ arg +"\"", new String[] { arg });
    int iName = c.getColumnIndex(KEY_NAME);
    String resulttwo = "";
    resulttwo = resulttwo + c.getString(iName);
    return resulttwo;
    }

Answer 1

我认为DATABASE_TABLE应该是一个变量：

String query = "select * from " + DATABASE_TABLE + " where title=\""+ arg +"\"";

还要考虑使用参数化查询来保护自己免受SQL注入攻击。

String query = "select * from " + DATABASE_TABLE + " where title=?";
Cursor c = ourDatabase.rawQuery(query, new String[] {arg});

或使用内置方法，例如SQLiteDatabase.query()

<强>加成

修改了代码，仍然是错误。

当您的应用崩溃时，您应该始终发布LogCat错误以及相关代码，但我可以立即看到错误。游标可以包含多个记录或者为空，您必须告诉Cursor 要读取哪个行并检查该行是否存在。为此，只需添加：

if (c.moveToFirst()) { /* return true if row exist, false if it doesn't */
    resulttwo = resulttwo + c.getString(iName);
}

如果要读取多行，请使用循环：

while (c.moveToFirst()) { 
    resulttwo = resulttwo + c.getString(iName);
}

还可以考虑直接使用StringBuilder或仅使用+=运算符。

Answer 2

而不是......

String query = "select * from DATABASE_TABLE where title=\""+ arg +"\"";
Cursor c = ourDatabase.rawQuery(query, null);

你可能想要像......这样的东西。

Cursor c = ourDatabase.rawQuery("select * from " + DATABASE_TABLE + " where title=?, new String[] { arg });

Android SQLite数据库：如何查询特定数据？

2 个答案: