Question

我创建了一个名为SetIP.java的独立java类，只需一个简单的打印：

package com.myname.appname;

import android.util.Log;

public class SetIP {

    public void hello(){
        Log.d("System", "Hello World!");
    }
}

在MainActivity中，我尝试通过以下方式调用它：

public class MainActivity extends AppCompatActivity {

    SetIP setip = new SetIP();
    setip.hello();
   // OnCreate and Stuff
}

但错误表示无法解析符号'Hello'。请帮忙。感谢

Answer 1

您需要在onCreate方法中调用它。

08:23:21,974 [-] [DataBridge-Core-pool-1-thread-2]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801943, data=[5, phone, g1, sell, samsung, iphone 4s, type, White 3 USB Port Car Charger Adapter For iPhone 4S 5S 5C 6 6S iPad Samsung Phone - Bid Now? sell, 27], isExpired=false} (Sanitized)
08:23:21,998 [-] [DataBridge-Core-pool-1-thread-4]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801944, data=[11, phone, g1, buy, samsung, galaxy s4, type, #cellular #deals  Samsung Galaxy S4 SCH-I545 16GB Verizon AT&amp;T GSM UNLOCKED Cell Phone RF buy, 27], isExpired=false} (Sanitized)
08:23:22,030 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801944, data=[13, phone, g1, sell, samsung, galaxy note, type, UNLOCKED T-Mobile Samsung Galaxy Note 3 SM-N900T 4G LTE GSM 32GB Smart Phone  sell, 27], isExpired=false} (Sanitized)
08:23:22,031 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801944, data=[18, phone, g1, sell, samsung, galaxy s6, type, Cell Phones : New Samsung Galaxy S6 Edge SM-G925F 5.1'' 16MP (FACTORY UNLOCKED) 32GB Phone  sell, 27], isExpired=false} (Sanitized)
08:23:22,031 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801944, data=[19, phone, g1, sell, samsung, galaxy s4, type, #cellular #deals  Samsung i545 Galaxy S4 16GB Verizon 13MP Camera WiFi Cell Phone sell, 27], isExpired=false} (Sanitized)
08:23:22,031 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801944, data=[1, phone, g1, sell, samsung, galaxy s6, type, Cell Phone USA : New Samsung Galaxy S6 Edge SM-G925F 5.1'' 16MP (FACTORY UNLOCKED) 32GB Ph?  sell, 27], isExpired=false} (Sanitized)
08:23:22,033 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801944, data=[14, phone, g1, sell, samsung, galaxy note, type, Galaxy Note 6 will reportedly be the first Samsung phone to feature USB-C -  sell, 27], isExpired=false} (Sanitized)
08:23:22,034 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801945, data=[16, phone, g1, buy, samsung, galaxy note, type, #unlocksquare Galaxy Note 6 will reportedly be the first Samsung phone to feature USB-C  buy, 27], isExpired=false} (Sanitized)
08:23:22,035 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801945, data=[17, phone, g1, buy, samsung, galaxy s5, type, Cell Phone USA : NEW T-Mobile Protective Cover/Holster For Samsung Galaxy S5 Case Kickstan?  buy, 27], isExpired=false} (Sanitized)
08:23:22,035 [-] [DataBridge-Core-pool-1-thread-5]  INFO TenantId : -1234, Event Processor : R_H_Match, Event Stream : RelatedStream:1.0.0 (rs), before processing _Event{timestamp=1464144801945, data=[15, phone, g1, buy, samsung, galaxy s6, type, Cell Phone USA : Samsung Galaxy S6 SM-G920F 32GB Unlocked 16MP Smartphone  #4422  buy, 27], isExpired=false} (Sanitized)

Answer 2

当你现在正在调用时，你不应该动态调用任何类的对象的方法，正如你告诉你的// OnCreate and Stuff低于对象的方法调用。

它必须是内部构造函数或一些方法，比如这里

SetIP setip = new SetIP();
@Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setip.hello();
   }

或

@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); SetIP setip = new SetIP(); setip.hello(); }

Answer 3

您可以将SetIP实例化为MainActivity的全局变量，但调用该函数仍应驻留在MainActivity的函数中。一个例子是将其置于onCreate活动中，如下所示

public class MainActivity extends AppCompatActivity {

    SetIP setip = new SetIP();

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

        setip.hello();
    }

    // Other Stuff
}

Answer 4

public class MainActivity extends AppCompatActivity {

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

      SetIP setip = new SetIP();
      setip.hello();
   }

   // Other methods
}

Answer 5

你需要改变只有方法是静态的

public class SetIP {    
    public static void hello(){
        Log.d("System", "Hello World!");
    }
}

尝试这项工作。

Android系统。如何从另一个文件访问类到MainActivity

5 个答案: