java - 在导航 View 中添加 ListView

Question

我在 Android Studio 中创建了一个抽屉导航 Activity。在抽屉导航的 xml 文件中有一个导航 View 并引用一个菜单。但我希望导航 View 引用 ListView 。我已经在 xml 中完成了它，但我得到一个错误，它说我引用的文本 id 创建我的列表项是在空对象上调用的。我该如何解决这个问题？

这是我的日志:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
        at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:399)
        at android.widget.ArrayAdapter.getView(ArrayAdapter.java:369)
        at android.widget.AbsListView.obtainView(AbsListView.java:2346)
        at android.widget.ListView.makeAndAddView(ListView.java:1876)
        at android.widget.ListView.fillDown(ListView.java:702)
        at android.widget.ListView.fillFromTop(ListView.java:763)
        at android.widget.ListView.layoutChildren(ListView.java:1685)
        at android.widget.AbsListView.onLayout(AbsListView.java:2148)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1221)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
        at com.android.internal.policy.PhoneWindow$DecorView.onLayout(PhoneWindow.java:2733)
        at android.view.View.layout(View.java:16668)
        at android.view.ViewGroup.layout(ViewGroup.java:5443)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2171)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1931)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6042)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:876)
        at android.view.Choreographer.doCallbacks(Choreographer.java:688)
        at android.view.Choreographer.doFrame(Choreographer.java:624)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:862)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:148)
        at android.app.ActivityThread.main(ActivityThread.java:5468)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

java代码:

 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        ...            

        View drawerLayout = (View) findViewById(R.id.nav_view);

        ArrayList<String> counters = new ArrayList<>();
        counters.add("Sayaç 1");
        counters.add("Sayaç 2");
        counters.add("Sayaç 3");
        counters.add("Sayaç 4");
        counters.add("Sayaç 5");

        ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, R.layout.activity_main, android.R.id.text1, counters);

        ListView listView = (ListView) findViewById(R.id.list);

        listView.setAdapter(arrayAdapter);



    }

  ...

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_camera) {
            // Handle the camera action
        } else if (id == R.id.nav_gallery) {

        } else if (id == R.id.nav_slideshow) {

        } else if (id == R.id.nav_manage) {

        } else if (id == R.id.nav_share) {

        } else if (id == R.id.nav_send) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

Answer 1

这里有问题:

ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, R.layout.activity_main, android.R.id.text1, counters);

param R.layout.activity_main 是项目布局的id，可能是android.R.layout.simple_list_item_1

应该是这样的:

ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, android.R.id.text1, counters);