当我尝试运行以下活动时出现错误。 该活动有一个自定义导航抽屉。 我是android新手.... 错误发生在涉及动作栏的地方。
当我尝试运行以下活动时出现错误。 该活动有一个自定义导航抽屉。 我是android新手.... 错误发生在涉及动作栏的地方。
当我尝试运行以下活动时出现错误。 该活动有一个自定义导航抽屉。 我是android新手.... 错误发生在涉及动作栏的地方。
import android.app.ActionBar;
import android.content.Context;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
public class HomeActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {
DrawerLayout drawer_layout;
ListView drawer_list;
ActionBarDrawerToggle drawer_toggle;
ActionBar abar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
drawer_layout= (DrawerLayout) findViewById(R.id.drawer_layout);
drawer_list= (ListView) findViewById(R.id.drawer_list);
drawer_list.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1));
drawer_list.setOnItemClickListener(this);
abar=getActionBar();
/*drawer_toggle = new ActionBarDrawerToggle(this, drawer_layout,
R.drawable.tick, R.string.app_name, R.string.app_name) {
*//** Called when a drawer has settled in a completely closed state. *//*
public void onDrawerClosed(View view) {
super.onDrawerClosed(view);
getActionBar().setTitle("Yuride");
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
*//** Called when a drawer has settled in a completely open state. *//*
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
getActionBar().setTitle("Yuride");
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
};*/
abar.setHomeButtonEnabled(true);
abar.setDisplayHomeAsUpEnabled(true);
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
}
class Myadapter extends BaseAdapter
{
Context context;
String[] drawer_items;
public Myadapter(Context context)
{
this.context=context;
drawer_items=context.getResources().getStringArray(R.array.drawer_items);
}
@Override
public int getCount() {
return drawer_items.length;
}
@Override
public Object getItem(int position) {
return drawer_items[position];
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row=null;
if(convertView==null)
{
LayoutInflater inflater= (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
row=inflater.inflate(R.layout.drawer_row,parent,false);
}
else
{
row=convertView;
}
ImageView drawer_icon= (ImageView) row.findViewById(R.id.drawer_icon);
TextView drawer_text= (TextView) row.findViewById(R.id.drawer_text);
drawer_text.setText(drawer_items[position]);
drawer_icon.setImageResource(R.drawable.tick);
return null;
}
}
}
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/drawer_layout">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
<ListView
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="left"
android:id="@+id/drawer_list">
</ListView>
</android.support.v4.widget.DrawerLayout>
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="in.yusoft.yuride.yuride">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".SplashActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".Entrance" />
<activity android:name=".HomeActivity"></activity>
</application>
</manifest>
java.lang.RuntimeException: Unable to start activity ComponentInfo{in.yusoft.yuride.yuride/in.yusoft.yuride.yuride.HomeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2622)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2683)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1440)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:6066)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:770)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:660)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference
at in.yusoft.yuride.yuride.HomeActivity.onCreate(HomeActivity.java:52)
at android.app.Activity.performCreate(Activity.java:6584)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2575)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2683)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1440)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:6066)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:770)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:660)
答案 0 :(得分：0)
问题在于设置ActionBar。 而不是
abar=getActionBar();
abar.setHomeButtonEnabled(true);
abar.setDisplayHomeAsUpEnabled(true);
用XML写：
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/drawer_layout">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true"
android:theme="@style/MyMaterialTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_collapseMode="pin"
app:popupTheme="@style/MyMaterialTheme.PopupOverlay" />
</android.support.design.widget.AppBarLayout>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
</FrameLayout>
<ListView
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="left"
android:id="@+id/drawer_list">
</ListView>
</android.support.v4.widget.DrawerLayout>
在setContentView（R.layout.activity_home）之后的Java类中;：
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
if(getSupportActionBar()!=null){
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}