工具栏后退按钮错误Android [英] toolbar back button error Android
本文介绍了工具栏后退按钮错误Android的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我想在我创建的工具栏中添加一个后退"按钮，因为我删除了默认按钮以使某些选项卡具有材质设计效果，但是每次添加代码使该按钮出现时，Android都会给出一个异常提示这个:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.juan.sdfnsdfnskdfnskdfmsfd, PID: 13348
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.support.v4.widget.DrawerLayout.getDrawerLockMode(int)' on a null object reference
at android.support.v7.app.ActionBarDrawerToggle.toggle(ActionBarDrawerToggle.java:284)
at android.support.v7.app.ActionBarDrawerToggle$1.onClick(ActionBarDrawerToggle.java:202)
at android.view.View.performClick(View.java:6308)
at android.view.View$PerformClick.run(View.java:23969)
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:6823)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1557)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1445)
如果我只在自己创建的工具栏中编写相应的代码，我将无法理解使用空对象引用的含义.
这是toolbar.xml:
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/toolbar_morado"
android:id="@+id/toolbar_lista_compras"
android:minHeight="?attr/actionBarSize">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/contador_toolbar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Lista de compras"
android:textSize="18sp"
android:textColor="#ffffff"/>
</RelativeLayout>
</android.support.v7.widget.Toolbar>
这是我实现工具栏的地方:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
android:id="@+id/appBarLayoutCalcular">
<include layout="@layout/toolbar"></include>
<android.support.design.widget.TabLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/tablayoutCalcular"
app:tabGravity="fill"
app:tabMode="fixed"
android:background="@color/toolbar_anaranjado"
app:tabTextAppearance="@style/myTabSize"
app:tabIndicatorColor="#5c1be1"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewPagerCalcular"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
这是我的课程:
public class CalculateMaterials extends AppCompatActivity{
DrawerLayout drawerLayout;
ActionBarDrawerToggle actionBarDrawerToggle;
Toolbar toolbar;
NavigationView navigationView;
TabLayout tabLayout;
ViewPager viewPager;
ViewPagerAdapter viewPagerAdapter;
String tabSeleccionado;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.calcular_materiales);
toolbar = (Toolbar)findViewById(R.id.toolbar_shopping_list);
toolbar.setBackgroundColor(ContextCompat.getColor(getApplicationContext(), R.color.toolbar_anaranjado));
setSupportActionBar(toolbar);
// text for the toolbar
TextView textoToolbar = (TextView)findViewById(R.id.contador_toolbar);
textoToolbar.setText("Calcular los materiales");
// status bar color
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
getWindow().setStatusBarColor(ContextCompat.getColor(getApplicationContext(), R.color.statusBar_anaranjado));
}
// adding toolbar back button
// this is where I have the error
if (toolbar != null) {
toolbar.setNavigationIcon(R.drawable.backButton);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onBackPressed();
}
});
}
drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close);
navigationView = (NavigationView)findViewById(R.id.navigationView);
tabLayout = (TabLayout)findViewById(R.id.tablayoutCalcular);
viewPager = (ViewPager)findViewById(R.id.viewPagerCalcular);
// adding the tabs
viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
viewPagerAdapter.addFragments(new FragmentCalcular(), "Con area");
viewPagerAdapter.addFragments(new FragmentCalcular2(), "Con metros");
viewPager.setAdapter(viewPagerAdapter);
tabLayout.setupWithViewPager(viewPager);
我也尝试:
// add back arrow to toolbar
if (getSupportActionBar() != null){
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
这也会产生相同的错误.
那么，有人可以帮助我解决这个问题吗?
修改
感谢所有尝试帮助我解决此问题的人.我终于找到了错误.
前一段时间，我试图在所有活动中添加一个NavigationView，但是我忘记删除该类中的必要代码，这就是为什么抽屉布局不出现在xml中的原因.
因此，当我删除抽屉布局变量时，一切正常！
解决方案
尝试一下
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onBackPressed();
}
});
I want to add a Back button in a toolbar that I created because I deleted the default one to have the material design effect with some tabs, but every time I add the code to make that button appear, Android gives an exception saying this:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.juan.sdfnsdfnskdfnskdfmsfd, PID: 13348
java.lang.NullPointerException: Attempt to invoke virtual method 'int android.support.v4.widget.DrawerLayout.getDrawerLockMode(int)' on a null object reference
at android.support.v7.app.ActionBarDrawerToggle.toggle(ActionBarDrawerToggle.java:284)
at android.support.v7.app.ActionBarDrawerToggle$1.onClick(ActionBarDrawerToggle.java:202)
at android.view.View.performClick(View.java:6308)
at android.view.View$PerformClick.run(View.java:23969)
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:6823)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1557)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1445)
I do not understand what it means with a null object reference if I only write the corresponding code in the toolbar that I created.
This is the toolbar.xml:
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/toolbar_morado"
android:id="@+id/toolbar_lista_compras"
android:minHeight="?attr/actionBarSize">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/contador_toolbar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Lista de compras"
android:textSize="18sp"
android:textColor="#ffffff"/>
</RelativeLayout>
</android.support.v7.widget.Toolbar>
This is where I implement the toolbar:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.design.widget.AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
android:id="@+id/appBarLayoutCalcular">
<include layout="@layout/toolbar"></include>
<android.support.design.widget.TabLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/tablayoutCalcular"
app:tabGravity="fill"
app:tabMode="fixed"
android:background="@color/toolbar_anaranjado"
app:tabTextAppearance="@style/myTabSize"
app:tabIndicatorColor="#5c1be1"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewPagerCalcular"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
This is my class:
public class CalculateMaterials extends AppCompatActivity{
DrawerLayout drawerLayout;
ActionBarDrawerToggle actionBarDrawerToggle;
Toolbar toolbar;
NavigationView navigationView;
TabLayout tabLayout;
ViewPager viewPager;
ViewPagerAdapter viewPagerAdapter;
String tabSeleccionado;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.calcular_materiales);
toolbar = (Toolbar)findViewById(R.id.toolbar_shopping_list);
toolbar.setBackgroundColor(ContextCompat.getColor(getApplicationContext(), R.color.toolbar_anaranjado));
setSupportActionBar(toolbar);
// text for the toolbar
TextView textoToolbar = (TextView)findViewById(R.id.contador_toolbar);
textoToolbar.setText("Calcular los materiales");
// status bar color
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
getWindow().setStatusBarColor(ContextCompat.getColor(getApplicationContext(), R.color.statusBar_anaranjado));
}
// adding toolbar back button
// this is where I have the error
if (toolbar != null) {
toolbar.setNavigationIcon(R.drawable.backButton);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onBackPressed();
}
});
}
drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close);
navigationView = (NavigationView)findViewById(R.id.navigationView);
tabLayout = (TabLayout)findViewById(R.id.tablayoutCalcular);
viewPager = (ViewPager)findViewById(R.id.viewPagerCalcular);
// adding the tabs
viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
viewPagerAdapter.addFragments(new FragmentCalcular(), "Con area");
viewPagerAdapter.addFragments(new FragmentCalcular2(), "Con metros");
viewPager.setAdapter(viewPagerAdapter);
tabLayout.setupWithViewPager(viewPager);
I also try with:
// add back arrow to toolbar
if (getSupportActionBar() != null){
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
That also gives the same error.
So, Can anyone help me with this problem?
Edit
Thanks to everyone who tried to help me with this problem. I finally found the error.
Some time ago, I tried to add a navigationView in all the activities, but I forgot to delete the necessary code in the class, that's why the drawerLayout doesnt appears in the xml.
So, when I delete the drawerLayout variable, everything works!
解决方案
Try this
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
onBackPressed();
}
});
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