java - 如何从一个 Activity 访问一个方法并将其用于 Android 中的另一个 Activity？

Question

我有第一个类名为iHave

public class iHave extends ActionBarActivity
{   

//below is the instance for calling the method from the other activity. 
(The name of the other activity is **iThank**)

**iThank thankYou = new iThank();**

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

    Button button = (Button) findViewById(R.id.button);

    button.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            **//this is the method I want to access from iThank class** **strong text**
            thankYou.display();
        }
    });       
} 

//下一个类是“iThank”

public class iThank extends ActionBarActivity
{

 @Override

protected void onCreate(Bundle savedInstanceState)
{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_i_thank);

        txtThank = (TextView) findViewById(R.id.textView3);

    //this is the method I want to access/use from iHave Activity 
    public void display()
    {
        txtThank.setText ("Shine");
    }
}

如何将 iThank Activity 的“public void display()”方法用于“iHave” Activity ？它总是给我一个 NullPointerException 错误。请帮忙。非常感谢!

Answer 1

How can I access a method from an activity and use it into another activity in Android?

通过创建对象供其他人从 Activity 访问方法是正确的方法。

使用LocalBroadcastManager用于应用程序组件之间的通信。

1. 单击按钮时从 iHave 发送广播:

@Override
   public void onClick(View v)
     {
       Intent intent = new Intent("DISPLAY_EVENT");
       LocalBroadcastManager.getInstance(v.getContext()).sendBroadcast(intent);
     }

2.在iThank Activity 中注册LocalBroadcastManager:

@Override
protected void onResume() {
    // TODO Auto-generated method stub
    super.onResume();
    LocalBroadcastManager.getInstance(this).registerReceiver(ReceiveMessage,
            new IntentFilter("DISPLAY_EVENT"));
}

3.在iThank Activity中创建BroadcastReceiver对象并调用display()方法:

private BroadcastReceiver ReceiveMessage = new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            // TODO Auto-generated method stub
             display();
        }
    };

还在 TextView 的显示方法中添加 null 检查:

public void display()
{   
   if(txtThank !=null)
    txtThank.setText ("Shine");
}