Android Studio 在片段中打开抽屉

Question

我从应用程序中删除了操作栏，所以我需要创建按钮来自己打开抽屉按钮 活动工作正常，但是当我在片段应用程序中使用它时停止工作(当我调用片段时)

我在活动中使用的代码(工作正常的代码)

ImageButton btn = (ImageButton)findViewById(R.id.drawerButton);
btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.openDrawer(Gravity.START);
}
});

fragment_achievements.xml

<android.support.constraint.ConstraintLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="layout.AchievementsFragment">
<ImageButton
android:id="@+id/imageButton"
android:layout_width="28dp"
android:layout_height="29dp"
android:layout_marginLeft="16dp"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:background="@android:color/transparent"
android:scaleType="fitCenter"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/ic_menu_button" />
<WebView
android:id="@+id/web_ach"
android:layout_width="409dp"
android:layout_height="602dp"
android:layout_marginBottom="-9dp"
android:layout_marginLeft="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
tools:layout_editor_absoluteY="56dp" />
</android.support.constraint.ConstraintLayout>

成就片段.java

package layout;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.widget.DrawerLayout;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ImageButton;
import th.ac.sd.sdschoolnd.R;
/**
* A simple {@link Fragment} subclass.
*/
public class AchievementsFragment extends Fragment {

public AchievementsFragment() {
// Required empty public constructor
}
public WebView mWebView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
//return inflater.inflate(R.layout.fragment_achievements, container, false);
// Inflate the layout for this fragment
//return inflater.inflate(R.layout.fragment_snews, container, false);
View v=inflater.inflate(R.layout.fragment_achievements, container, false);
mWebView = (WebView) v.findViewById(R.id.web_ach);
mWebView.loadUrl("http://www.sd.ac.th/main/wp-content/WebApps/android/rss_achievements.html");
WebSettings webSettings = mWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
// Force links and redirects to open in the WebView instead of in a browser
mWebView.setWebViewClient(new WebViewClient());
ImageButton button = (ImageButton) getView().findViewById(R.id.drawerButton);
button.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
DrawerLayout drawer = (DrawerLayout) getView().findViewById(R.id.drawer_layout);
drawer.openDrawer(Gravity.START);
}
});
return v;
}
}

错误日志

[ 03-10 16:27:00.791 22121:22160 D/         ]
HostConnection::get() New Host Connection established 0x947f8c00, tid 22160
03-10 16:27:00.794 22121-22161/th.ac.sd.sdschoolnd E/chromium: [ERROR:gles2_cmd_decoder.cc(2210)] [GroupMarkerNotSet(crbug.com/242999)!:546A05A2]GL ERROR :GL_INVALID_OPERATION : BackFramebuffer::Create: <- error from previous GL command
03-10 16:27:00.798 22121-22160/th.ac.sd.sdschoolnd W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
03-10 16:27:00.798 22121-22160/th.ac.sd.sdschoolnd D/OpenGLRenderer: Swap behavior 0
03-10 16:27:00.857 22121-22121/th.ac.sd.sdschoolnd W/art: Attempt to remove non-JNI local reference, dumping thread
03-10 16:27:00.950 22121-22121/th.ac.sd.sdschoolnd W/art: Attempt to remove non-JNI local reference, dumping thread
03-10 16:27:00.984 22121-22121/th.ac.sd.sdschoolnd W/cr_BindingManager: Cannot call determinedVisibility() - never saw a connection for the pid: 22121
03-10 16:27:03.877 22121-22121/th.ac.sd.sdschoolnd W/art: Attempt to remove non-JNI local reference, dumping thread
03-10 16:27:03.895 22121-22121/th.ac.sd.sdschoolnd W/cr_AwContents: onDetachedFromWindow called when already detached. Ignoring
03-10 16:27:03.897 22121-22121/th.ac.sd.sdschoolnd I/cr_Ime: ImeThread is not enabled.
03-10 16:27:03.902 22121-22161/th.ac.sd.sdschoolnd E/chromium: [ERROR:gles2_cmd_decoder.cc(2210)] [GroupMarkerNotSet(crbug.com/242999)!:546F05A2]GL ERROR :GL_INVALID_OPERATION : BackFramebuffer::Create: <- error from previous GL command
03-10 16:27:03.902 22121-22121/th.ac.sd.sdschoolnd D/AndroidRuntime: Shutting down VM
03-10 16:27:03.902 22121-22121/th.ac.sd.sdschoolnd E/AndroidRuntime: FATAL EXCEPTION: main
Process: th.ac.sd.sdschoolnd, PID: 22121
java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
   at layout.AchievementsFragment.onCreateView(AchievementsFragment.java:44)
   at android.support.v4.app.Fragment.performCreateView(Fragment.java:2189)
   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1299)
   at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1528)
   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1595)
   at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:757)
   at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2355)
   at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2146)
   at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2098)
   at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2008)
   at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:710)
   at android.os.Handler.handleCallback(Handler.java:751)
   at android.os.Handler.dispatchMessage(Handler.java:95)
   at android.os.Looper.loop(Looper.java:154)
   at android.app.ActivityThread.main(ActivityThread.java:6119)
   at java.lang.reflect.Method.invoke(Native Method)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

Answer 1

那是因为你试图在fragment中找到drawerLayout，这不是在片段中，而是在你的activity中。
这是你的错误——DrawerLayout drawer = (DrawerLayout) getView().findViewById(R.id.drawer_layout);

而是在活动中创建方法，并从fragment调用该方法

这将是您的活动中的方法

public void openDrawer() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.openDrawer(Gravity.START);
}

现在从你的片段调用此方法 -

((YourActivity) getActivity()).openDrawer();

最后，您的片段代码将是：-

button.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
((YourActivity) getActivity()).openDrawer();
}
});

Answer 2

在抽屉所在的主活动中声明这一点，如下所示

public DrawerLayout drawer;

以及与上述相同的活动(主要活动)onCreate

drawer = (DrawerLayout) findViewById(R.id.drawer_layout);

在仅附加到您的主要活动的片段中

button.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
((MainActivity) getActivity()).drawer.openDrawer(Gravity.START);
}
});

Answer 3

试试这个

button.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick(View v)
{
DrawerLayout drawer = (DrawerLayout) getActivity().findViewById(R.id.drawer_layout);
drawer.openDrawer(Gravity.START);
}
});

Answer 4

从片段与其活动进行通信的最佳方式是通过接口。 片段中包括：

private AchievementsFragment.OnFragmentInteractionListener mListener;
public interface OnFragmentInteractionListener {
void openDrawer();
void closeDrawer();
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}

从您想打开片段中抽屉的任何地方，您可以调用

mListener.openDrawer();

确保在您的活动中实现侦听器和函数 openDrawer 和 closeDrawer

public class NavDrawerActivity extends AppCompatActivity
implements AchievementsFragment.OnFragmentInteractionListener{
//some code
}

Answer 5

在 Kotlin 中，它将是

在活动中添加方法

fun openDrawer() {
val drawer = findViewById<View>(R.id.drawerLayout) as DrawerLayout
drawer.openDrawer(Gravity.LEFT, true)
}

在片段中调用方法

(activity as MyActivity?)?.openDrawer()

打开抽屉，希望对某人有所帮助