在其他活动中调用方法或字符串

Question

I had an Activity that contains a String,Method etc. I want to read it using another Activity. Here is my code.

Activitymain.java

public class Activitymain extends Activity{

public String input;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.act_main);
        input = "This is the input";
}

The other Activity.

SecondAct.java

public class SecondAct extends Activity{

        @Override
            protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.secon_act);
                Activitymain am = (Activitymain) this;
                Toast.maketext(this, ""+am.input,Toast.LENGTH_LONG).show();
        }

But it crashes when I go to the other Activity. Here is the log:

11-14 14:42:45.000: E/AndroidRuntime(16457): FATAL EXCEPTION: main
11-14 14:42:45.000: E/AndroidRuntime(16457): java.lang.NullPointerException
11-14 14:42:45.000: E/AndroidRuntime(16457):    at com.example.tabs.SecondAct.Start_Call(SecondAct.java:384)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at com.example.tabs.SecondAct$1.onClick(SecondAct.java:420)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:946)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.widget.AdapterView.performItemClick(AdapterView.java:298)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.widget.AbsListView.performItemClick(AbsListView.java:1114)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:2933)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.widget.AbsListView$1.run(AbsListView.java:3691)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.os.Handler.handleCallback(Handler.java:615)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.os.Handler.dispatchMessage(Handler.java:92)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.os.Looper.loop(Looper.java:153)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at android.app.ActivityThread.main(ActivityThread.java:5086)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at java.lang.reflect.Method.invokeNative(Native Method)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at java.lang.reflect.Method.invoke(Method.java:511)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
11-14 14:42:45.000: E/AndroidRuntime(16457):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

Try this in SecondAct.java:

public class SecondAct extends Activity{

        @Override
            protected void onCreate(Bundle savedInstanceState) {
               super.onCreate(savedInstanceState);
                setContentView(R.layout.secon_act);                
                Toast.maketext(this, ""+Activitymain.input,Toast.LENGTH_LONG).show();
        }

And don't forget to initiate input string in Activitymain .

Answer 2

There is lots of ways to do this.

First: You can pass the data in bundle when you are starting the SecondAct from Activitymain.

Second: Create a global static variable somewhere. Set it in Activitymain and get it in SecondAct.

Third: Create a singleton class for your whole application to store the data in Activitymain and get that data from SecondAct.

Check out this post if you are interested Singleton Example