小编Moh*_*Ali的帖子

我试图检查sqlite数据库是否为空

public boolean chkDB(){
        boolean chk = false;
        Cursor mCursor = db.rawQuery("SELECT * FROM " + DATABASE_TABLE, null);
        if (mCursor != null){
            mCursor.moveToFirst();
            if (mCursor.getInt(0) == 0){
                chk = false;
            }
        }else{
            chk = true;
        }
        return chk;
    }

但每次我调用该方法我都会得到空指针异常

我的Logcat显示了这个

06-28 22:35:19.519: E/AndroidRuntime(441):  at com.android.id.DBAdapter.chkDB(DBAdapter.java:82)
06-28 22:58:06.269: E/AndroidRuntime(621): FATAL EXCEPTION: main
06-28 22:58:06.269: E/AndroidRuntime(621): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.id/com.android.id.MainActivity}: java.lang.NullPointerException
06-28 22:58:06.269: E/AndroidRuntime(621):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
06-28 22:58:06.269: E/AndroidRuntime(621):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
06-28 22:58:06.269: E/AndroidRuntime(621):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
06-28 22:58:06.269: E/AndroidRuntime(621): …

我正在使用本教程中的代码来裁剪图像

Intent intent = new Intent(Intent.ACTION_GET_CONTENT, null);
                    intent.setType("image/*");
                    intent.putExtra("crop", "true");
                    intent.putExtra("aspectX", aspectX);
                    intent.putExtra("aspectY", aspectY);
                    intent.putExtra("outputX", outputX);    
                    intent.putExtra("outputY", outputY);
                    intent.putExtra("scale", scale);
                    intent.putExtra("return-data", return_data);
                    intent.putExtra(MediaStore.EXTRA_OUTPUT, getTempUri());
                    intent.putExtra("outputFormat", Bitmap.CompressFormat.JPEG.toString());

但我想修改三角形(用于确定要裁剪的区域)的纵横比,使x轴更长y轴