Question

我正在尝试使AnotherActivity扩展主FullscreenActivity，但我发现错误，没有空的构造函数

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.terrh/com.example.terrh.FullscreenActivity$AnotherActivity}: java.lang.InstantiationException: can't instantiate class com.example.terrh.FullscreenActivity$AnotherActivity; no empty constructor

所以我试图添加它，但不正确。

FulscreenActivity.java

public class FullscreenActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ihkj);
    }

    public void buttonClicked(View button) {
        Intent intent = new Intent(this, AnotherActivity.class);
        startActivity(intent);
    }

    public class AnotherActivity extends FullscreenActivity {
        public AnotherActivity() {
        }

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.another);
        }    
    }
}

的Manifest.xml

<activity
        android:name="com.example.terrh.FullscreenActivity"
        android:configChanges="orientation|keyboardHidden|screenSize"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.example.terrh.FullscreenActivity$AnotherActivity"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.NoTitleBar.Fullscreen">
        <intent-filter >
            <action  android:name="in.wptrafficanalyzer.AnotherActivity"/>
            <category  android:name="android.intent.category.DEFAULT"/>
        </intent-filter>
    </activity>

如何正确添加空构造函数以使其正常工作，还是可以用其他方式解决此问题？

Answer 1

首先，当不需要扩展Activity时，你无法创建默认构造函数。如果要获取anotherActivity类的公共函数，则创建该类的静态方法getInstance（）。见下面的代码：

public static Activity activity;

public void onCreate (...){
   ....
   ....
  activity=anotherActivity.this;
}

public static anotherActivity getInstance(){
   return activity;
}

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AnotherActivity如何扩展MainActivity

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