如何从一个Java类调用start活动 [英] how to call the start activity from one java class

问题描述

是否可以在extends Activity的通用java类中使用Intent来启动Activty?

Is it possible to start an Activty using an Intent in a general java class which extends Activity?

 import android.os.Bundle;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.Spinner;
 import android.app.Activity;
 import android.content.Intent;

 public class SubActivity extends Activity{

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

还有一个通用的Java类，如下所示:

And a general java class like the following

class TestClass extends Activity{

       void firstsem(){
        Intent t = new Intent(this, SubActivity.class);
        t.putExtra("sub1","chemistry");                 
        startActivity(t);
   }
}

是否可以从一般的Java类启动Activity?有人可以告诉我如何实现这一目标吗?

Is it possible to start an Activity from an general java class? Could anybody show me how to achieve this?

推荐答案

要启动Activity，您需要Context.

方法startActivity(Intent intent)继承自Context类. 在文档中可以看到

另外，显式的Intent本身在其构造函数中也需要一个Context.

Also an explicit Intent itself needs a Context in its constructor.

Intent(Context packageContext, Class<?> cls)

与Activity extends Context一样，您已经扩展了Activity，可以将自己的类用作Context. 因此只需调用

As Activity extends Context and you've extended Activity you can use your own class as Context. And thus simply call

void method() {
    startActivity(new Intent(this, ActivityName.class));
} 

如果您不想扩展Activity，可以将Context作为参数传递.

If you do not want to extend Activity you can pass the Context as an argument.

public static void startActivity(Context context) {
    context.startActivity(new Intent(context, ActivityName.class));
} 

基本实现

public class ActivityA extends Activity {

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate();
    }

    public void onClick(View view) {
        ActivityStarter.startActivityB(this);
    }
}

public class ActivityB extends Activity {

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate();
    }
}

public class ActivityStarter {

    public static void startActivityB(Context context) {
        Intent intent = new Intent(context, ActivityB.class);
        intent.putExtra("sub1","chemistry"); 
        context.startActivity(intent);
    }
}

这篇关于如何从一个Java类调用start活动的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！