将导航抽屉活动扩展到其他活动

Question

我正在尝试创建一个导航抽屉活动，以便我可以扩展该活动，并按照此问题中给出的答案链接所有活动中的菜单但是我的测试应用程序一直在崩溃，这是我的代码：

BaseActivity.java

public class BaseActivity extends Activity {

    public DrawerLayout drawerLayout;
    public ListView drawerList;
    public String[] layers;
    private ActionBarDrawerToggle drawerToggle;

    protected void onCreate(Bundle savedInstanceState) {
        // R.id.drawer_layout should be in every activity with exactly the same
        // id.
        drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);

        drawerToggle = new ActionBarDrawerToggle((Activity) this, drawerLayout,
                R.drawable.ic_drawer, 0, 0) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(R.string.hello_world);
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(R.string.hello_world);
            }
        };
        drawerLayout.setDrawerListener(drawerToggle);

        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        layers = getResources().getStringArray(R.array.planets_array);
        drawerList = (ListView) findViewById(R.id.left_drawer);
        drawerList.setAdapter(new ArrayAdapter<String>(this,
                R.layout.drawer_list_item, android.R.id.text1, layers));

    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        if (drawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        return super.onOptionsItemSelected(item);

    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        drawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        drawerToggle.onConfigurationChanged(newConfig);
    }
}

MainActivity.java

public class MainActivity extends BaseActivity {

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

}

activity_profile.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".ProfileActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

logcat的

03-03 01:22:18.031: D/AndroidRuntime(27902): Shutting down VM
03-03 01:22:18.031: W/dalvikvm(27902): threadid=1: thread exiting with uncaught exception (group=0x2b542210)
03-03 01:22:18.041: E/AndroidRuntime(27902): FATAL EXCEPTION: main
03-03 01:22:18.041: E/AndroidRuntime(27902): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.slider/com.example.slider.MainActivity}: java.lang.NullPointerException
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1967)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1992)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.ActivityThread.access$600(ActivityThread.java:127)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1158)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.os.Looper.loop(Looper.java:137)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.ActivityThread.main(ActivityThread.java:4441)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at java.lang.reflect.Method.invokeNative(Native Method)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at java.lang.reflect.Method.invoke(Method.java:511)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at dalvik.system.NativeStart.main(Native Method)
03-03 01:22:18.041: E/AndroidRuntime(27902): Caused by: java.lang.NullPointerException
03-03 01:22:18.041: E/AndroidRuntime(27902):    at com.example.slider.BaseActivity.onCreate(BaseActivity.java:35)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at com.example.slider.MainActivity.onCreate(MainActivity.java:12)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.Activity.performCreate(Activity.java:4465)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
03-03 01:22:18.041: E/AndroidRuntime(27902):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1931)
03-03 01:22:18.041: E/AndroidRuntime(27902):    ... 11 more

Answer 1

问题似乎是基类不知道布局。 不知道如何或为什么它为其他人工作而不必做这样的事情..但我是Android新手。

我得到了同样的错误，并通过onCreate将我的布局传递给基础解决了。

所以在基础上，我修改onCreate是这样的：

protected void onCreate(Bundle savedInstanceState, int resLayoutID)
{
    super.onCreate(savedInstanceState);
    setContentView(resLayoutID);

然后，从我的新活动，我有这个：

@Override
protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState, R.layout.my_activity);

我的基础中的代码现在可以工作而不是保持为null：

drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
drawerList = (ListView) findViewById(R.id.left_drawer);

顺便说一句，这个结果是朋友向我推荐的，它对我有用。

Answer 2

在main活动中，你必须在setContentView（）之后调用super.onCreate（savedInstanceState）

Answer 3

在父classBaseActivity上 ：

• 声明一个protected abstract int getLayoutId();

• onCreate（）我添加了这一行

   setContentView(getLayoutId()); 

现在在您的子类MainActivity上实现它，如：

 protected int getLayoutId() {
    return R.layout.activity_profile;
}

如果您知道更好的解决方案，请告诉我。

Answer 4

正如oli所建议的那样，您需要在主活动中调用setContentView（R.layout.activity_view） 。

一旦设置了Main Activity中的内容视图，就必须调用BaseActivity的onCreate ，如下所示：

public class BaseActivity extends Activity {
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // REST Navigation drawer initialization
    }

}



public class MainActivity extends BaseActivity {

    protected void onCreate(Bundle savedInstanceState) {

        setContentView(R.layout.activity_view);
        super.onCreate(savedInstanceState);

        // REST APPLICATION CODE
    }
}

Answer 5

你的xml文件看起来应该是这样的，取自android网站： http ： //developer.android.com/training/implementing-navigation/nav-drawer.html

<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- The main content view -->
    <FrameLayout
        android:id="@+id/content_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
        <!-- Add content here -->
    </FrameLayout>

    <!-- The navigation drawer -->
    <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="#111"/>
</android.support.v4.widget.DrawerLayout>

Answer 6

在你MainActivity中之前只需设置setContentView(R.layout.activity_main)

super.onCreate(savedInstanceState);

如下：

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