Question

我得到一个DrawerLayout无法投射错误，我的应用程序崩溃。我是新手android帮帮我

这是我的主要活动

public class MainActivity extends AppCompatActivity {

private Toolbar toolbar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    toolbar = (Toolbar) findViewById(R.id.app_bar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayShowHomeEnabled(true);
    NavigationDrawerFragment drawerFragment = (NavigationDrawerFragment)
        getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);
    drawerFragment.setUp((DrawerLayout) findViewById(R.id.drawer_layout),toolbar);

}


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

}

这是Activitymain.xml

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


<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <include
        android:id="@+id/app_bar"
        layout="@layout/app_bar" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/app_bar"

        android:text="@string/hello_world" />

</RelativeLayout>

<fragment
    android:id="@+id/fragment_navigation_drawer"
    android:name="com.appdego.rosesketch.NavigationDrawerFragment"
    android:layout_width="@dimen/nav_drawer_width"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    app:layout="@layout/fragment_navigation_drawer"
    tools:layout="@layout/fragment_navigation_drawer" />

我的NavigationDrawerFragment.java代码

public class NavigationDrawerFragment extends Fragment {

private ActionBarDrawerToggle mDrawerToggle;
private DrawerLayout mDrawerLayout;

public NavigationDrawerFragment() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_navigation_drawer, container, false);
}


public void setUp(DrawerLayout drawerLayout, Toolbar toolbar) {
    mDrawerLayout = drawerLayout;
    mDrawerToggle = new ActionBarDrawerToggle(getActivity(), (DrawerLayout) drawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close) {
        @Override
        public void onDrawerOpened(View drawerView) {
            super.onDrawerOpened(drawerView);
        }

        @Override
        public void onDrawerClosed(View drawerView) {
            super.onDrawerClosed(drawerView);
        }
    };
    mDrawerLayout.setDrawerListener((DrawerListener) mDrawerLayout);
}

}

和fragment_navigation_drawer.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"
tools:context="com.appdego.rosesketch.NavigationDrawerFragment">

<!-- TODO: Update blank fragment layout -->
<TextView android:layout_width="match_parent" android:layout_height="match_parent"
    android:text="@string/hello_blank_fragment" />

logcat的：

    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.appdego.rosesketch/com.appdego.rosesketch.MainActivity}: java.lang.ClassCastException: android.support.v4.widget.DrawerLayout cannot be cast to android.support.v4.widget.DrawerLayout$DrawerListener
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2338)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
        at android.app.ActivityThread.access$800(ActivityThread.java:151)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
        at android.os.Handler.dispatchMessage(Handler.java:110)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:5292)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.ClassCastException: android.support.v4.widget.DrawerLayout cannot be cast to android.support.v4.widget.DrawerLayout$DrawerListener
        at com.appdego.rosesketch.NavigationDrawerFragment.setUp(NavigationDrawerFragment.java:49)
        at com.appdego.rosesketch.MainActivity.onCreate(MainActivity.java:25)
        at android.app.Activity.performCreate(Activity.java:5264)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088)

我遵循slidenerd材料设计教程

Answer 1

问题在于这一行：mDrawerLayout.setDrawerListener((DrawerListener) mDrawerLayout);您需要设置一个侦听器，但是您要将DrawerLayout输入到DrawerListener。

我建议您完全删除该行，因为它不需要。如果你真的想设置一个监听器，你应该按如下方式进行：

       mDrawerLayout.setDrawerListener(new DrawerLayout.DrawerListener() {
            @Override
            public void onDrawerSlide(View drawerView, float slideOffset) {

            }

            @Override
            public void onDrawerOpened(View drawerView) {

            }

            @Override
            public void onDrawerClosed(View drawerView) {

            }

            @Override
            public void onDrawerStateChanged(int newState) {

            }
        });

Answer 2

您需要在下面更改代码：

  // Set the drawer toggle as the DrawerListener
        mDrawerLayout.setDrawerListener(mDrawerToggle);

android.support.v4.widget.DrawerLayout无法强制转换为android.support.v4.widget.DrawerLayout $ DrawerListener

2 个答案: