从图库中选择图像后出现空白屏幕

Posted 2023-02-22

【中文标题】从图库中选择图像后出现空白屏幕

【英文标题】：Blank Screen showing up after Image Selected from Gallery

【发布时间】：2021-08-13 01:29:44

【问题描述】：

我正在尝试将图像放入 ImageView，但每当我单击图库中的图片时，应用程序都会显示一个空白屏幕并关闭。 这个 ImageView 在一个片段中

public View onCreateView(LayoutInflater inflater, ViewGroup 容器, 捆绑保存的InstanceState） 查看 v = inflater.inflate(R.layout.fragment_auction_add, container, false);

    auction_add_imageViewButton = v.findViewById(R.id.auction_add_imageView_button);

    auction_add_imageViewButton.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 
            imageSelectAction(v);
        
    );


    dateTimeAction(v);


    return v;


private void imageSelectAction(View v) 
    auction_add_imageViewButton = v.findViewById(R.id.auction_add_imageView_button);
    auction_add_image = v.findViewById(R.id.auction_add_imageView);

    choosePicture();



private void choosePicture() 
    Intent intent = new Intent();
    intent.setType("image/*");
    intent.setAction(Intent.ACTION_GET_CONTENT);
    startActivityForResult(Intent.createChooser(intent, "Select Picture"), SELECT_PICTURE);


@Override
public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) 
    super.onActivityResult(requestCode, resultCode, data);

    if (resultCode == Activity.RESULT_OK) 
        if (requestCode == SELECT_PICTURE) 
            if (data != null && data.getData() != null) 
                Uri selectedImageUri = data.getData();

                auction_add_image.setImageURI(selectedImageUri);
            
        
    

初始声明

public class auction_add extends Fragment 


    private static final int SELECT_PICTURE = 10;
    private static final int PERMISSION_CODE = 11;
    ImageButton auction_add_imageViewButton;


    //References to all Auction Add Page EditText
    EditText auction_add_itemNameTxt;
    EditText auction_add_descriptionTxt;
    EditText auction_add_initialPriceTxt;
    EditText auction_add_startTimeTxt;
    EditText auction_add_endTimeTxt;

    //Reference to ImageView
    private ImageView auction_add_image;

    final Calendar myCalendar = Calendar.getInstance();

感谢您的帮助，谢谢！

编辑：

接下来是android Studio的运行选项卡上的错误

W/System: A resource failed to call close. 
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.projectcrest, PID: 5618
    java.lang.RuntimeException: Failure delivering result ResultInfowho=null, request=242868079, result=-1, data=Intent  dat=content://com.android.providers.media.documents/document/image:31 flg=0x1  to activity com.example.projectcrest/com.example.projectcrest.pages.LandingPage: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageURI(android.net.Uri)' on a null object reference
        at android.app.ActivityThread.deliverResults(ActivityThread.java:5015)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:5056)
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageURI(android.net.Uri)' on a null object reference
        at com.example.projectcrest.fragments.auction_add.onActivityResult(auction_add.java:155)
        at androidx.fragment.app.FragmentManager$9.onActivityResult(FragmentManager.java:2905)
        at androidx.fragment.app.FragmentManager$9.onActivityResult(FragmentManager.java:2885)
        at androidx.activity.result.ActivityResultRegistry.doDispatch(ActivityResultRegistry.java:377)
        at androidx.activity.result.ActivityResultRegistry.dispatchResult(ActivityResultRegistry.java:336)
        at androidx.activity.ComponentActivity.onActivityResult(ComponentActivity.java:624)
        at androidx.fragment.app.FragmentActivity.onActivityResult(FragmentActivity.java:164)
        at android.app.Activity.dispatchActivityResult(Activity.java:8310)
        at android.app.ActivityThread.deliverResults(ActivityThread.java:5008)
        at android.app.ActivityThread.handleSendResult(ActivityThread.java:5056) 
        at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:51) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7656) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 
I/Process: Sending signal. PID: 5618 SIG: 9

【问题讨论】：

by shows a blank screen and closes down This ImageView is in a fragment 声明，你的意思是应用选择图片/照片后关闭？

是的，这就是我的意思，很抱歉造成混乱

当应用程序以这种方式关闭时意味着出现问题并引发异常。您能否查看 Android Logcat 并尝试在此处发布错误消息？错误消息将有助于提供正确的解决方案。

我在帖子上添加了一个编辑并放了错误信息

【参考方案1】：

通过查看异常，似乎由于 NPE（空指针异常），应用程序在 auction_add_image.setImageURI(selectedImageUri); 行的 #onActivityResult 函数中崩溃。这种预期/崩溃是由于 auction_add_image 对象具有 null 值而不是 ImageView。

仔细查看您的代码后，我认为问题是由于以下代码引起的：

    auction_add_imageViewButton = v.findViewById(R.id.auction_add_imageView_button);

    auction_add_imageViewButton.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 
            imageSelectAction(v);
        
    );

请注意，在#onClick 函数中，您将传递视图v，您将在该视图上执行#findViewById 操作。这里传递的视图v 指的是auction_add_imageViewButton，而不是您在上面捕获的v。

我建议修改如下代码（只需在#onClick 函数中重命名v 变量）：

    auction_add_imageViewButton = v.findViewById(R.id.auction_add_imageView_button);

    auction_add_imageViewButton.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View buttonView) 
            imageSelectAction(v);
        
    );

这样可以避免变量名冲突并解决错误。

另外，如果这不能解决您的问题，请检查 #findViewById 是否返回 ImageView 而不是 null。如果提供给#findViewById 的Id 不存在于屏幕上或视图的子视图（在其上执行#findViewById）中，则#findViewById 将返回空值。

另外，检查您是否在代码中的任何位置为auction_add_image 分配了空值。

【讨论】：

感谢这解决了参考文献混乱的问题