Cursor多线程操作下的错误

Cursor多线程操作下的异常
E/AndroidRuntime(28116): java.lang.NullPointerExceptionE/AndroidRuntime(28116): at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:144)E/AndroidRuntime(28116): at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:133)E/AndroidRuntime(28116): at com.letv.signalsourcemanager.MainActivity.handleScanCompleted(MainActivity.java:1728)E/AndroidRuntime(28116): at com.letv.signalsourcemanager.MainActivity.access$1200(MainActivity.java:88)E/AndroidRuntime(28116): at com.letv.signalsourcemanager.MainActivity$10.onReceive(MainActivity.java:2570)E/AndroidRuntime(28116): at android.support.v4.content.LocalBroadcastManager.executePendingBroadcasts(LocalBroadcastManager.java:297)E/AndroidRuntime(28116): at android.support.v4.content.LocalBroadcastManager.access$000(LocalBroadcastManager.java:46)E/AndroidRuntime(28116): at android.support.v4.content.LocalBroadcastManager$1.handleMessage(LocalBroadcastManager.java:116)E/AndroidRuntime(28116): at android.os.Handler.dispatchMessage(Handler.java:99)E/AndroidRuntime(28116): at android.os.Looper.loop(Looper.java:137)E/AndroidRuntime(28116): at android.app.ActivityThread.main(ActivityThread.java:4777)E/AndroidRuntime(28116): at java.lang.reflect.Method.invokeNative(Native Method)E/AndroidRuntime(28116): at java.lang.reflect.Method.invoke(Method.java:511)E/AndroidRuntime(28116): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)E/AndroidRuntime(28116): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)E/AndroidRuntime(28116): at dalvik.system.NativeStart.main(Native Method)W/ActivityManager( 635): Force finishing activity com.letv.signalsourcemanager/.MainActivity

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?? 查看SQLiteCursor源码发现，

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    @Override    public int getCount() {        if (mCount == NO_COUNT) {            fillWindow(0);        }        return mCount;    }    private void fillWindow(int requiredPos) {        clearOrCreateWindow(getDatabase().getPath());        if (mCount == NO_COUNT) {            int startPos = DatabaseUtils.cursorPickFillWindowStartPosition(requiredPos, 0);            mCount = mQuery.fillWindow(mWindow, startPos, requiredPos, true);            mCursorWindowCapacity = mWindow.getNumRows();            if (Log.isLoggable(TAG, Log.DEBUG)) {                Log.d(TAG, "received count(*) from native_fill_window: " + mCount);            }        } else {            int startPos = DatabaseUtils.cursorPickFillWindowStartPosition(requiredPos,                    mCursorWindowCapacity);            mQuery.fillWindow(mWindow, startPos, requiredPos, false);        }    }

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???

具体是getCount的时候现判断

mCount == NO_COUNT

实际上此时cursor的count是大于0的，然后进入了fillWindow，然后在

mCursorWindowCapacity = mWindow.getNumRows();

出现了空指针错误。

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??? 由于现象是偶现的，所以我就判定跟多线程有关，导致Cursor的问题。

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?? 那么就需要加同步锁来解决了。具体方式有很多，此处不赘述。

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