Question

我制作了仅包含ListView的布局。在我的主要布局中，我有一个按钮。单击该按钮后，我需要带有ListView的布局以弹出包含ListView的项目。 ListView将从数据库中读取数据，但目前我只处理伪数据。

我尝试将数组适配器传递给ListView，但它总是告诉我它是一个空对象。

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tableview);


        //machines
        machinesListButton = findViewById(R.id.machine_show);


        final ArrayList<String> arrayList = new ArrayList<>();







        machinesListButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                arrayList.add("test1");
                arrayList.add("test2");

                Dialog dialog = new Dialog(FileActivity.this);
                dialog.setContentView(R.layout.activity_file_machines_list);
                dialog.setTitle("title");
                dialog.setCancelable(true);

                machinesListView = findViewById(R.id.machinesListView);
                ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(getApplicationContext(),android.R.layout.simple_list_item_1,arrayList);
                machinesListView.setAdapter(arrayAdapter);

                machinesListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                    }
                });

                dialog.show();

            }
        });
    }

这是错误：

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.mobics.medical, PID: 32538
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
        at com.example.mobics.medical.FileActivity$1.onClick(FileActivity.java:110)
        at android.view.View.performClick(View.java:6597)
        at android.view.View.performClickInternal(View.java:6574)
        at android.view.View.access$3100(View.java:778)
        at android.view.View$PerformClick.run(View.java:25889)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6692)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)enter code here

Answer 1

您可以尝试：

machinesListView = dialog.findViewById(R.id.machinesListView);

这是因为您的列表视图ID R.id.machinesListView处于这种布局activity_tableview

弹出一个包含ListView的窗口

1 个答案: