Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()

报错信息：Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()

报错原因：由于在类中直接实例化对象

具体错误实例：直接在实体类中初始化ArrayAdapter 

public class MainActivity extends Activity implements SearchView.OnQueryTextListener {
    // 自动完成的列表
    private final String[] mStrings = { "aaaaa", "bbbbbb", "cccccc", "ddddddd" };
    //自适应
    public ArrayAdapter adapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, mStrings)；

    @Override
    protected void onCreate(Bundle savedInstanceState) {
      
    }
}

正确解决方法：

• 第一步：在类中定义：ArrayAdapter<String> adapter;
• 第二步：在onCreate方法中将这个ArrayAdapter实例化

修改方法：

public class MainActivity extends Activity implements SearchView.OnQueryTextListener {
    // 自动完成的列表
    private final String[] mStrings = { "aaaaa", "bbbbbb", "cccccc", "ddddddd" };
    //自适应
    public ArrayAdapter adapter；

    @Override
    protected void onCreate(Bundle savedInstanceState) {
　　　　adapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, mStrings)；

 } 
}