Question

我正在尝试使我的数据库可读，考虑到只检索了选中的“categoria”，所以我开发了这段代码：

plus = praia+ cafe+serv+rest+hot+muse+mon+escolas;
String dados[] = new String[plus];

//categoria is the name of the colum
String query = "categoria = ?";

for (i = 1; i < plus; i++) {
    query = query+ " OR categoria = ?";
}

//if == 1 its active if == 0 its unactive;
if (praia == 1) {
   dados[cont]= "Praias";
}

if (serv == 1) {
   dados[cont]= "Servicos";
}

if (cafe == 1) {
   dados[cont]= "Cafes";
}

if (rest == 1) {
   dados[cont]= "Restaurantes";
}

if (hot == 1) {
   dados[cont]= "Hoteis";
}

if (muse == 1) {
   dados[cont]= "Museus";
}

if (mon == 1) {
   dados[cont]= "Monumentos";
}

if (escolas == 1) {
   dados[cont]= "Escolas";
}

String[] projections ={VianaContract.NewLocalInfo.Nome, VianaContract.NewLocalInfo.Categoria, VianaContract.NewLocalInfo.Latitude, VianaContract.NewLocalInfo.Longitude};

//error here
cursor = db.query(VianaContract.NewLocalInfo.Table_name, projections, query, dados, null, null, null);

这是logcat：

05-01 07:58:13.131    1435-1435/prosis.guiatour D/AndroidRuntime﹕ Shutting down VM
05-01 07:58:13.131    1435-1435/prosis.guiatour W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb3ac7ba8)
 05-01 07:58:13.171    1435-1435/prosis.guiatour E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: prosis.guiatour, PID: 1435
java.lang.RuntimeException: Unable to start activity ComponentInfo{prosis.guiatour/prosis.guiatour.Lista}: java.lang.IllegalArgumentException: the bind value at index 3 is null
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.IllegalArgumentException: the bind value at index 3 is null
        at android.database.sqlite.SQLiteProgram.bindString(SQLiteProgram.java:164)
        at android.database.sqlite.SQLiteProgram.bindAllArgsAsStrings(SQLiteProgram.java:200)
        at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:47)
        at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
        at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1161)
        at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1032)
        at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1200)
        at prosis.guiatour.VianaDbHelper.getInfor(VianaDbHelper.java:123)
        at prosis.guiatour.Lista.onCreate(Lista.java:49)
        at android.app.Activity.performCreate(Activity.java:5231)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)    at android.app.ActivityThread.access$800(ActivityThread.java:135)    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)    at android.os.Handler.dispatchMessage(Handler.java:102)    at android.os.Looper.loop(Looper.java:136)    at android.app.ActivityThread.main(ActivityThread.java:5017)    at java.lang.reflect.Method.invokeNative(Native Method)    at java.lang.reflect.Method.invoke(Method.java:515)    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)    at dalvik.system.NativeStart.main(Native Method)

您认为导致错误的原因是什么？

Answer 1

问题在于，您正在为SQL数据库提供一个数组，以用作具有空绑定的条件。这意味着您的数组dados具有空值，数据库会看到并抛出异常。这是因为您初始化dados数组的方式。

查看您的代码，我看不到cont初始化的位置，但我会假设您将其设置为零。现在我遇到的问题是你永远不会增加cont，而是将它用作dados数组中某个位置的每个赋值的索引。如您所见，这只是意味着您每次都覆盖相同的位置，因此假设所有这些值都是1，您将拥有一个大小为8的数组，但只有cont的位置才会包含任何数据它和你的数组看起来像

{ Escolas, null, null, null, null, null, null, null }

到数据库，它必须抛出异常。

要解决此问题，只需按以下方式递增cont：

plus = praia + cafe + serv + rest + hot + muse + mon + escolas;
String dados[] = new String[plus];

// categoria is the name of the column
String query = "categoria = ?";

for(i = 1; i < plus; i++){
    query = query + " OR categoria = ?";
}

//if == 1 its active if == 0 its unactive;
cont = 0;

if(praia == 1){
    dados[cont] = "Praias";
    cont++;
}

if(serv == 1){
    dados[cont] = "Servicos";
    cont++;
}

if(cafe == 1){
   dados[cont] = "Cafes";
   cont++;
}

if(rest == 1){
   dados[cont] = "Restaurantes";
   cont++;
}

if(hot == 1){
   dados[cont] = "Hoteis";
   cont++;
}

if(muse == 1){
   dados[cont] = "Museus";
   cont++;
}

if(mon == 1){
   dados[cont] = "Monumentos";
   cont++;
}

if(escolas == 1){
   dados[cont] = "Escolas";
   cont++;
}

String[] projections ={VianaContract.NewLocalInfo.Nome, VianaContract.NewLocalInfo.Categoria, VianaContract.NewLocalInfo.Latitude, VianaContract.NewLocalInfo.Longitude};
cursor = db.query(VianaContract.NewLocalInfo.Table_name, projections, query, dados, null, null, null);

请告诉我这是否适合您。

Android数据库Sqlite用多个where检索数据

1 个答案: