Question

我试图从我的sqlite数据库中显示3个随机图像，但每次运行时应用程序总是崩溃。有谁能够帮我？感谢

这是我的代码：

 public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        doSync();
        int id = 0;
        Uri uri = Uri.withAppendedPath(Uri.withAppendedPath( LooserProvider.CONTENT_URI, Database.Project.NAME), Long .toString(id));

        Cursor managedCursor = managedQuery( uri, new String[] { BaseColumns._ID, Database.Project.C_BIGIMAGE }, null, null, "RANDOM() LIMIT 3");

        ImageView img = (ImageView) findViewById(R.id.top1);
        String imageUrl = managedCursor.getString(1);
        img.setTag(imageUrl);
        loader.DisplayImage(imageUrl, this, img);
}
    void doSync() {
    Intent serviceIntent = new Intent(this, LooserSync.class);
    startService(serviceIntent);
}

这是堆栈跟踪：

05-30 12:00:23.319: ERROR/AndroidRuntime(333): Uncaught handler: thread main exiting due to uncaught exception
05-30 12:00:23.319: ERROR/AndroidRuntime(333): java.lang.RuntimeException: Unable to start activity ComponentInfo{spendino.de/spendino.de.MainNew}: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 0
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2496)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.app.ActivityThread.access$2200(ActivityThread.java:119)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.os.Looper.loop(Looper.java:123)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.app.ActivityThread.main(ActivityThread.java:4363)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at java.lang.reflect.Method.invokeNative(Native Method)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at java.lang.reflect.Method.invoke(Method.java:521)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at dalvik.system.NativeStart.main(Native Method)
05-30 12:00:23.319: ERROR/AndroidRuntime(333): Caused by: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 0
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:214)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:41)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.database.CursorWrapper.getString(CursorWrapper.java:135)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at spendino.de.MainNew.onCreate(MainNew.java:69)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459)
05-30 12:00:23.319: ERROR/AndroidRuntime(333):     ... 11 more

已更新 所以我做了这个，但应用程序仍然崩溃：

if (uri != null) {
                Cursor cursor = managedQuery( uri, new String[] { BaseColumns._ID, Database.Project.C_BIGIMAGE }, null, null, "RANDOM() LIMIT 3");
                if (cursor == null) {
                    finish();
                } else {
                    //if (cursor.moveToFirst()) {
                        cursor.moveToFirst();
                        ImageView img = (ImageView) findViewById(R.id.top1);
                        String imageUrl = cursor.getString(0);
                        img.setTag(imageUrl);
                        loader.DisplayImage(imageUrl, this, img);

                    //} else {
                        //finish();
                    //}

                }

这是stacktrace

05-30 13:14:07.649: ERROR/AndroidRuntime(1064): Caused by: java.lang.NullPointerException
05-30 13:14:07.649: ERROR/AndroidRuntime(1064):     at spendino.de.MainNew.onCreate(MainNew.java:76)

此行的NullPointer：loader.DisplayImage(imageUrl, this, img); 但是，当我使用System.Out.println为每个变量调试时，没有任何内容为空。

有人知道为什么吗？

Answer 1

首先，使用try{} catch(){}块来阻止应用崩溃。堆栈跟踪非常简单：您对managedCursor.getString(1);的调用的索引超出范围，managedCursor为空或managedCursor.getString(1);不存在且应为managedCursor.getString(0); < / p>

Answer 2

Cursor managedCursor = managedQuery( uri, new String[] { BaseColumns._ID, Database.Project.C_BIGIMAGE }, null, null, "RANDOM() LIMIT 3");

if (managedCursor.getCount() > 0){
    ImageView img = (ImageView) findViewById(R.id.top1);
    String imageUrl = managedCursor.getString(1);
    img.setTag(imageUrl);
    loader.DisplayImage(imageUrl, this, img);
}

Answer 3

检查游标是否为空。如果它不为null，则将其移动到第一个位置，然后您可以检查行数。

if(managedCursor!=null) {
    managedCursor.moveToFirst();
    System.out.println("number of rows returned = "+managedCursor.getCount());
}

在使用光标和SQlite显示图像时崩溃

3 个答案: