我在Android Studio中创建了导航抽屉Activity。在导航抽屉的xml文件中，有一个导航视图，并引用一个菜单。但我希望导航视图能够引用列表视图。我已经在xml中完成了它，但是我得到一个错误，它表示我引用的文本ID在null对象上调用我的列表项。我怎么能解决这个问题？
这是我的logcat：
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;
}
}
答案 0 :(得分：1)
这里出了点问题：
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);
答案 1 :(得分：1)
您的ListView权限内有NavigationView吗？所以在这种情况下，你需要找到像这样的ListView。
在onCreate功能
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
// .. Your code
// And here's your list
ListView listView = (ListView) navigationView.getHeaderView(0).findViewById(R.id.list);
listView.setAdapter(arrayAdapter);
在ListView
NavigationView