Android 对特定行的数据库查询

我正在构建一个血库数据库应用程序。在那里我会带上一些血型信息。我将血型存储为“整数非空”，其中1、2、…、7表示A+、…、AB-血型。但是，当我试图根据用户从微调器中选择血型来查询listview时，会出现错误（下面给出了堆栈跟踪）。在数据库中插入数据做得很好，但没有给出错误

main活动

相关代码-

private void displayDatabaseInfo(){

        String[] projection = {
                DonorEntry.COLUMN_DONOR_NAME,
                DonorEntry.COLUMN_DONOR_MOBILE,
                DonorEntry.COLUMN_BLOOD_GROUP,
                DonorEntry.COLUMN_DONATE_DATE };

        String selection = DonorEntry.COLUMN_BLOOD_GROUP + "=?";

        String [] selectionArgs = new String[] {getString(mBloodType)};

        Cursor cursor = getContentResolver().query(DonorEntry.CONTENT_URI,
                projection, selection, selectionArgs,null);

        ListView listView = (ListView) findViewById(R.id.list);

        DonorCursorAdapter adapter = new DonorCursorAdapter(this, cursor);

        listView.setAdapter(adapter);
    }

DonorCursorAdapter

相关代码-

@Override
    public void bindView(View view, Context context, Cursor cursor) {
        // Find individual views that we want to modify in the list item layout
        TextView nameTextView = (TextView) view.findViewById(R.id.name);
        TextView mobileTextView = (TextView) view.findViewById(R.id.mobileNo);
        TextView bloodTypeTextView = (TextView) view.findViewById(R.id.bloodType);
        TextView lastDonateTextView = (TextView) view.findViewById(R.id.donateDate);

        // Find the columns of donor's attributes that we're interested in
        int nameColumnIndex = cursor.getColumnIndex(DonorEntry.COLUMN_DONOR_NAME);
        int mobileColumnIndex = cursor.getColumnIndex(DonorEntry.COLUMN_DONOR_MOBILE);
        int bloodTypeColumnIndex = cursor.getColumnIndex(DonorEntry.COLUMN_BLOOD_GROUP);
        int lastDonateColumnIndex = cursor.getColumnIndex(DonorEntry.COLUMN_DONATE_DATE);

        // Read the donor attributes from the Cursor for the current pet
        String donorName = cursor.getString(nameColumnIndex);
        String donorMobileNo = cursor.getString(mobileColumnIndex);
        String donorBloodType = cursor.getString(bloodTypeColumnIndex);
        String donorLastDonate = cursor.getString(lastDonateColumnIndex);

        // Update the TextViews with the attributes for the current pet
        nameTextView.setText(donorName);
        mobileTextView.setText(donorMobileNo);
        bloodTypeTextView.setText(donorBloodType);
        lastDonateTextView.setText(donorLastDonate);
    }

堆栈跟踪

<code>
2019-03-02 17:25:37.140 28705-28705/com.sarkerjr.greenBlood E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.sarkerjr.greenBlood, PID: 28705
    android.content.res.Resources$NotFoundException: String resource ID #0x2
        at android.content.res.Resources.getText(Resources.java:339)
        at android.content.res.Resources.getString(Resources.java:433)
        at android.content.Context.getString(Context.java:556)
        at com.sarkerjr.greenBlood.MainActivity.displayDatabaseInfo(MainActivity.java:121)
        at com.sarkerjr.greenBlood.MainActivity.access$000(MainActivity.java:21)
        at com.sarkerjr.greenBlood.MainActivity$2.onClick(MainActivity.java:56)
        at android.view.View.performClick(View.java:6294)
        at android.view.View$PerformClick.run(View.java:24770)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

</code>

召唤

String [] selectionArgs = new String[] {String.valueOf(mBloodType)};

而不是

String [] selectionArgs = new String[] {getString(mBloodType)};

---

这里为你修好了一切。有一些问题

getString

正在崩溃。这不是您要用来解析任何整数的方法，它用于获取

资源

，并传递该资源的

id

CursorAdapter

needs

\u id

列位于

cursor

中，当您通过

projection

数组而没有

\u id

列时，您的适配器崩溃。所以我删除了投影，现在你将得到所有的列

虽然这在某种程度上起了作用，但当列值类型为

INTEGER

时，不应该使用

getString

，因此我将其更改为

getInt

您直接将列值分配给显示整数的

TextView

，因此我在

MainActivity

中创建了一个方法来获取血型的实际值

main活动

更改-

private void displayDatabaseInfo() {

    String selection = DonorEntry.COLUMN_BLOOD_GROUP + "=?";

    String[] selectionArgs = new String[]{String.valueOf(mBloodType)};

    Cursor cursor = getContentResolver().query(DonorEntry.CONTENT_URI,
            null, selection, selectionArgs, null);

    ListView listView = findViewById(R.id.list);

    DonorCursorAdapter adapter = new DonorCursorAdapter(this, cursor);

    listView.setAdapter(adapter);
}

// Get value of readable blood type
public String getBloodTypeString(int bloodType) {
    switch (bloodType) {
        case A_Positive:
            return getResources().getString(R.string.a_positive);
        case A_Negative:
            return getResources().getString(R.string.a_negative);
        case B_Positive:
            return getResources().getString(R.string.b_positive);
        case B_Negative:
            return getResources().getString(R.string.b_negative);
        case O_Positive:
            return getResources().getString(R.string.o_positive);
        case O_Negative:
            return getResources().getString(R.string.o_negative);
        case AB_Positive:
            return getResources().getString(R.string.ab_positive);
        case AB_Negative:
            return getResources().getString(R.string.ab_negative);
        default:
            return "UNKNOWN";

    }
}

int donorBloodType = cursor.getInt(bloodTypeColumnIndex);

String donorBloodTypeString;
    try {
        donorBloodTypeString = ((MainActivity) context).getBloodTypeString(donorBloodType);
    } catch (ClassCastException e) {
        throw new ClassCastException("Trying to access MainActivity method from different context");
    }

bloodTypeTextView.setText(donorBloodTypeString);

DonorCursorAdapter

更改-

private void displayDatabaseInfo() {

    String selection = DonorEntry.COLUMN_BLOOD_GROUP + "=?";

    String[] selectionArgs = new String[]{String.valueOf(mBloodType)};

    Cursor cursor = getContentResolver().query(DonorEntry.CONTENT_URI,
            null, selection, selectionArgs, null);

    ListView listView = findViewById(R.id.list);

    DonorCursorAdapter adapter = new DonorCursorAdapter(this, cursor);

    listView.setAdapter(adapter);
}

// Get value of readable blood type
public String getBloodTypeString(int bloodType) {
    switch (bloodType) {
        case A_Positive:
            return getResources().getString(R.string.a_positive);
        case A_Negative:
            return getResources().getString(R.string.a_negative);
        case B_Positive:
            return getResources().getString(R.string.b_positive);
        case B_Negative:
            return getResources().getString(R.string.b_negative);
        case O_Positive:
            return getResources().getString(R.string.o_positive);
        case O_Negative:
            return getResources().getString(R.string.o_negative);
        case AB_Positive:
            return getResources().getString(R.string.ab_positive);
        case AB_Negative:
            return getResources().getString(R.string.ab_negative);
        default:
            return "UNKNOWN";

    }
}

int donorBloodType = cursor.getInt(bloodTypeColumnIndex);

String donorBloodTypeString;
    try {
        donorBloodTypeString = ((MainActivity) context).getBloodTypeString(donorBloodType);
    } catch (ClassCastException e) {
        throw new ClassCastException("Trying to access MainActivity method from different context");
    }

bloodTypeTextView.setText(donorBloodTypeString);

---

它崩溃是因为cursor.getString（bloodTypeColumnIndex）我相信。您正在数据库中存储

Integer

值，但试图从该列索引中获取字符串。因此，请尝试将其更改为

cursor.getInt（）

，然后使用

String.valueOf（）

将int解析为String。@Ranjan我进行了修改，但在int donorBloodType=cursor.getInt（bloodTypeColumnIndex）中无效；bloodTypeTextView.setText（String.valueOf（donorBloodType））；