我已经在这里待了几个小时，似乎根本无法让抽屉出现。这是我的代码，也许有人可以告诉我这里出了什么问题......该应用程序运行没有错误，直到我进入抽屉的活动，然后它崩溃了。
这是我的代码：
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;
import android.support.v7.app.ActionBarDrawerToggle;
public class FlavorListView extends ActionBarActivity {
//shared preference
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
@Override
public boolean onCreateOptionsMenu(Menu action_setting) {
//MenuInflater inflater = getMenuInflater();
//inflater.inflate(R.menu.menu_welcome,action_setting);
//drawer
mTitle = mDrawerTitle = getTitle();
mDrawerLayout = (DrawerLayout) findViewById(R.id.navigation_drawer);
mDrawerToggle = new ActionBarDrawerToggle(FlavorListView.this, mDrawerLayout,
R.string.drawer_open, R.string.drawer_close) {
/** Called when a drawer has settled in a completely closed state. */
public void onDrawerClosed(View view) {
super.onDrawerClosed(view);
getSupportActionBar().setTitle(mTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
/** Called when a drawer has settled in a completely open state. */
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
getSupportActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
};
// Set the drawer toggle as the DrawerListener
mDrawerLayout.setDrawerListener(mDrawerToggle);
return true;
}
/* Called whenever we call invalidateOptionsMenu() */
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
//boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
//menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
//return super.onPrepareOptionsMenu(menu);
//drawer end
return true;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.select_flavor);
String[] select_flavor_list = {"Kansas City", "Memphis", "Texas", "North Carolina", "South Carolina","Alabama"};
ListAdapter FlavorListAdapter = new ArrayAdapter<String>(this, R.layout.row_layout_flavor, R.id.flavor_text_view,
select_flavor_list);
ListView listView = (ListView) findViewById(R.id.listView);
listView.setAdapter(FlavorListAdapter);
//For list view selection, begin here...
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
//String flavorPicked = String.valueOf(parent.getItemAtPosition(position));
FoodStyleDialog cdd = new FoodStyleDialog(FlavorListView.this);
cdd.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
cdd.show();
return true;
}
});
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View v, int position, long id) {
//GlobalClass flavorPref = ((GlobalClass)getApplicationContext());
String flavorPicked = String.valueOf(adapterView.getItemAtPosition(position));
if (flavorPicked.equals("Kansas City")) {
Intent intent = new Intent(FlavorListView.this, KansasCity.class);
startActivity(intent);
setContentView(R.layout.kansas_city);
Toast.makeText(FlavorListView.this, "Looks like " + flavorPicked +
" style be your flavor! You can change your flavor anytime in the settings menu.",
Toast.LENGTH_LONG).show();
}
else if (flavorPicked.equals("Memphis")) {
Intent intent = new Intent(FlavorListView.this, KansasCity.class);
startActivity(intent);
setContentView(R.layout.kansas_city);
Toast.makeText(FlavorListView.this, "Looks like " + flavorPicked +
" style be your flavor! You can change your flavor anytime in the settings menu.",
Toast.LENGTH_LONG).show();
}
}
});
}
}
我得到了一个java.lang.NullPointerException，调试器在(FlavorListView.java:57)说这是mDrawerLayout.setDrawerListener(mDrawerToggle);
如果我注释出这一行，应用程序会运行但没有抽屉......
请帮忙。谢谢:)
抽屉布局 xml：
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/navigation_drawer"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- As the main content view, the view below consumes the entire
space available using match_parent in both dimensions. -->
<FrameLayout
android:id="@+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<!-- android:layout_gravity="start" tells DrawerLayout to treat
this as a sliding drawer on the left side for left-to-right
languages and on the right side for right-to-left languages.
The drawer is given a fixed width in dp and extends the full height of
the container. A solid background is used for contrast
with the content view. -->
<ListView
android:id="@+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="@android:color/transparent"
android:dividerHeight="0dp"
android:background="#ffff"/>
</android.support.v4.widget.DrawerLayout>
FlavorListView Acivity xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:paddingBottom="16dp"
android:paddingTop="16dp"
tools:context=".FlavorListView"
>
<TextView
android:layout_width="match_parent"
android:layout_height="40dp"
android:text="Choose Your Flavor"
android:textAlignment="center"
android:textSize="30sp"
android:textStyle="bold"
android:gravity="center_horizontal"
/>
<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/listView"
android:listSelector="@drawable/abc_list_pressed_holo_light" />
</LinearLayout>
如果你在那里得到一个 NPE，那么mDrawerLayout必须为 null。确保drawer_layout是正确的 ID 才能在 XML 中查找抽屉。您还需要膨胀抽屉布局XML文件。你几乎是正确的（你需要用你的文件名替换下面的menu_welcome）：
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_welcome, action_setting);
mDrawerLayout = (DrawerLayout) action_setting.findViewById(R.id.navigation_drawer);
将下面的代码放在您的onCreate中，而不是放在
onCreateOptionMenu
/------------------------------------------------------------/
mTitle = mDrawerTitle = getTitle();
mDrawerLayout = (DrawerLayout) findViewById(R.id.navigation_drawer);
mDrawerToggle = new ActionBarDrawerToggle(FlavorListView.this, mDrawerLayout,R.drawable.ic_menu,
R.string.drawer_open, R.string.drawer_close) {
/** Called when a drawer has settled in a completely closed state. */
public void onDrawerClosed(View view) {
super.onDrawerClosed(view);
getSupportActionBar().setTitle(mTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
/** Called when a drawer has settled in a completely open state. */
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
getSupportActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
};
// Set the drawer toggle as the DrawerListener
mDrawerLayout.setDrawerListener(mDrawerToggle);
使用前请仔细阅读示例代码