android - 如何在 android 的 actionbar 中设置自定义 View ？

Question

我想在操作栏应用程序标题中使用自定义字体，但每次我遇到相同的错误(空指针异常)并且我的应用程序告诉我“不幸的是 **** 已停止”。我搜索了很多并尝试使用它们。但是没有任何效果。同样的错误不断发生。我创建了一个带有 TextView 的简单布局，并尝试通过这一行将其插入操作栏中

ActionBar actionBar = getActionBar();
actionBar.setCustomView(R.layout.custom_actionbar);

无论我做什么，setCustomView 都会向我发送空指针错误。我在想，如果我可以在 actionbar 中设置布局，那么更改 TextView 字体将很容易。这是我的完整代码。

public class MainActivity extends ActionBarActivity {
    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @Override
    protected void onCreate(Bundle savedInstanceState) {

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

        ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
        viewPager.setAdapter(new ViewPagerAdapter(getSupportFragmentManager()));
        ActionBar actionBar = getActionBar();
        actionBar.setCustomView(R.layout.custom_actionbar);

    }
}

和布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/transparent" >

    <TextView
        android:id="@+id/App_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_marginLeft="10dp"
        android:textSize="40dp"
        android:maxLines="2"
        android:ellipsize="end"
        android:text="Prime" />
</RelativeLayout>

和错误:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tushar.primeplay2/com.example.tushar.primeplay2.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2306)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
            at android.app.ActivityThread.access$600(ActivityThread.java:156)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1340)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5297)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.example.tushar.primeplay2.MainActivity.onCreate(MainActivity.java:22)
            at android.app.Activity.performCreate(Activity.java:5122)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
            at android.app.ActivityThread.access$600(ActivityThread.java:156)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1340)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5297)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)

我正在使用安卓工作室。

Answer 1

试试这个

如果你正在使用支持库

ActionBar actionBar = getActionBar();

否则

ActionBar actionBar = getSupportActionBar();

然后

LayoutInflater inflator = (LayoutInflater) this .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = inflator.inflate(R.layout.custom_actionbar, null);
actionBar.setCustomView(v);

你的 onCreate 应该是这样的

public class MainActivity extends ActionBarActivity {
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@Override
protected void onCreate(Bundle savedInstanceState) {

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

    ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
    viewPager.setAdapter(new ViewPagerAdapter(getSupportFragmentManager()));
    ActionBar actionBar = getSupportActionBar(); // As you said you are using support library
    LayoutInflater inflator = (LayoutInflater) this .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View v = inflator.inflate(R.layout.custom_actionbar, null);
    actionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
    actionBar.setCustomView(v);

}
}

记得导入

import android.support.v7.app.ActionBar

而不是

import android.app.ActionBar