Question

所以我的代码遇到了这个错误我正在使用androidx，我认为问题是因为dat。老实说，我不知道如何更改为旧版本的android

所以错误是这个

error: incompatible types: androidx.appcompat.widget.Toolbar cannot be converted to android.widget.Toolbar

我已经尝试导入android.support.v7.wigdet.Toolbar不起作用：（

MainActivity.Java

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;



import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

        Toolbar toolbar = findViewById(R.id.toolbar);
        setActionBar(toolbar);
    }

nav_header.xml

activity_main.xml

Build.gradle

运行时更新错误

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.readytogo, PID: 8403
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.readytogo/com.example.readytogo.MainActivity}: android.view.InflateException: Binary XML file line #26 in com.example.readytogo:layout/activity_main: Binary XML file line #26 in com.example.readytogo:layout/activity_main: Error inflating class fragment
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3260)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3396)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2009)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7319)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:934)
     Caused by: android.view.InflateException: Binary XML file line #26 in com.example.readytogo:layout/activity_main: Binary XML file line #26 in com.example.readytogo:layout/activity_main: Error inflating class fragment
     Caused by: android.view.InflateException: Binary XML file line #26 in com.example.readytogo:layout/activity_main: Error inflating class fragment
     Caused by: java.lang.NullPointerException
        at java.lang.VMClassLoader.findLoadedClass(Native Method)
        at java.lang.ClassLoader.findLoadedClass(ClassLoader.java:738)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:363)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at android.app.Fragment.instantiate(Fragment.java:536)
        at android.app.FragmentContainer.instantiate(FragmentContainer.java:53)
        at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:3553)
        at android.app.FragmentController.onCreateView(FragmentController.java:104)
        at android.app.Activity.onCreateView(Activity.java:6929)
        at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:326)
        at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1069)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:997)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:961)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:1123)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1084)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:1126)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1084)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:682)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:534)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:481)
        at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:470)
        at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:141)
        at com.example.readytogo.MainActivity.onCreate(MainActivity.java:16)
        at android.app.Activity.performCreate(Activity.java:7783)
        at android.app.Activity.performCreate(Activity.java:7772)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3235)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3396)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2009)
E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7319)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:934)

Answer 1

如果您希望使用androidx依赖项，则您的代码必须如下所示

放入您的activity_main.xml

<com.google.android.material.appbar.AppBarLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/app_bar"
            android:theme="@style/AppTheme.AppBarOverlay">

            <androidx.appcompat.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/AppTheme.PopupOverlay" />

</com.google.android.material.appbar.AppBarLayout>

您的MainActivty.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }
}

在您的app.gradle内部使用androidx依赖项，如下所示

 implementation 'androidx.appcompat:appcompat:1.1.0-alpha02'

我希望这对您有用，请让我知道。

Answer 2

我想您必须在这里使用setSupportActionBar(yourToolbar)。

Answer 3

尝试一下

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;



import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }
}

当您从AppComatActivity而不是Activity扩展时，因此必须使用setSupportActionBar而不是setActionBar。

在您的xml工具栏中也丢失了，您需要在活动xml中添加工具栏，例如

    <androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:titleTextAppearance="@style/ToolBarStyle" />

Answer 4

确保您的XML中有类似这样的内容

然后您可以进行类似的操作

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

在setActionBar（）上出现一些错误

4 个答案: