java.lang.NullPointerException：当我从数据库中删除图像时出现uriString

Question

我创建了一个 ListView，它将显示我的数据库子项。如果我点击它，我将有一个 AlertDialog 询问我是否要删除图像。

删除图像后，我将尝试转到显示 ListView 的活动，它与日志一起崩溃：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.user.alphaver, PID: 5739
    java.lang.NullPointerException: uriString
        at android.net.Uri$StringUri.<init>(Uri.java:496)
        at android.net.Uri$StringUri.<init>(Uri.java:486)
        at android.net.Uri.parse(Uri.java:458)
        at com.example.alphaver.ImagesActivity$1.populateView(ImagesActivity.java:61)
        at com.firebase.ui.database.FirebaseListAdapter.getView(FirebaseListAdapter.java:121)
        at android.widget.AbsListView.obtainView(AbsListView.java:2405)
        at android.widget.ListView.makeAndAddView(ListView.java:2071)
        at android.widget.ListView.fillDown(ListView.java:797)
        at android.widget.ListView.fillFromTop(ListView.java:859)
        at android.widget.ListView.layoutChildren(ListView.java:1814)
        at android.widget.AbsListView.onLayout(AbsListView.java:2202)
        at android.view.View.layout(View.java:21912)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:21912)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:21912)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at androidx.appcompat.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:446)
        at android.view.View.layout(View.java:21912)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:21912)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:21912)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:779)
        at android.view.View.layout(View.java:21912)
        at android.view.ViewGroup.layout(ViewGroup.java:6260)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3080)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2590)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1721)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7598)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
        at android.view.Choreographer.doCallbacks(Choreographer.java:790)
        at android.view.Choreographer.doFrame(Choreographer.java:725)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:951)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

这是导致崩溃的我的 ListView 代码，但我不知道为什么：

lv = (ListView)findViewById(R.id.lv);
    Query query = FirebaseDatabase.getInstance().getReference().child("Uploads");
    FirebaseListOptions<Upload> options  = new FirebaseListOptions.Builder<Upload>()
            .setLayout(R.layout.information)
            .setLifecycleOwner(ImagesActivity.this)
            .setQuery(query, Upload.class)
            .build();
    adapter = new FirebaseListAdapter(options) {
        @Override
        protected void populateView(@NonNull View v, @NonNull Object model, int position) {

            TextView name = v.findViewById(R.id.name_tv);
            ImageView imageView = v.findViewById(R.id.imageViewTV);

            Upload std = (Upload) model;
            name.setText(std.getName());

            if(Uri.parse(std.getmImageUrl()) != null){
            Picasso.get().load(Uri.parse(std.getmImageUrl())).into(imageView);
            }


        }
    };

我正在寻求解决问题并在没有 mImageUrl 值显示时让 ListView 不显示任何内容。

Answer 1

看起来std.getmImageUrl() 在没有 URL 时返回 null，而 Uri.parse 无法处理。

简单的解决方案是为 null 添加额外检查：

if(std.getmImageUrl() != null && Uri.parse(std.getmImageUrl()) != null){
    Picasso.get().load(Uri.parse(std.getmImageUrl())).into(imageView);
}