Question

我正在尝试将一些内容设置到操作栏，但我在使用的任何方法上都会遇到相同的错误（例如actionBar.setTitle("my title");或actionBar.setBackgroundDrawable(R.drawable.actionbar_draw);）

我甚至无法使用get方法...

他们都给出了这个错误：

required android.support.v7.app.ActionBar but found android.app.ActionBar

我使用的是最小sdk 15，这是我的代码：

    package com.tos.test.testactionbarapp;

    import android.support.v7.app.ActionBar;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;

    public class MainActivity extends AppCompatActivity {



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

        ActionBar actionBar = getActionBar();
        actionBar.setTitle("my title");


    }
}

问题是，我的应用程序因为这个代码而无法启动它，我得到：

---

------ beginning of crash 05-28 15:32:00.403 11476-11476/ccom.tos.test.testactionbarapp E/AndroidRuntime: FATAL EXCEPTION: main Process: com.tos.test.testactionbarapp, PID: 11476 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tos.test.testactionbarapp/com.tos.test.testactionbarapp.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.app.ActionBar.getTitle()' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) at android.app.ActivityThread.access$800(ActivityThread.java:151) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5254) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.CharSequence android.app.ActionBar.getTitle()' on a null object reference at com.tos.test.testactionbarapp.MainActivity.onCreate(MainActivity.java:21) at android.app.Activity.performCreate(Activity.java:5990) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) at android.app.ActivityThread.access$800(ActivityThread.java:151) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5254) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Answer 1

更改

getActionBar();

到

getSupportActionBar();

试一试!!

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

ActionBar actionBar = getSupportActionBar();
actionBar.setTitle("my title");


}

Answer 2

您必须import android.support.v7.app.ActionBar并使用getSupportActionBar()方法od活动。

Answer 3

做这个

ActionBar actionBar = getSupportActionBar();

而不是

ActionBar actionBar = getActionBar();

无法在android studio

3 个答案: