SubActivites with return value - The InputBox

plusminus · by **plusminus** » Sat Nov 24, 2007 1:35 pm

What you learn: You will learn how to start a SubActivity, that will return a String (+ extra Data), what is in the end exactly like an InputBox.

:?:

Problems/Questions: Write them right below...

Difficulty: 1 of 5

What it will look like:

Description
This has been a very common question, as in "normal" Java you can make a blocking a MessageBox was displayed with code like:

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public static String JOptionPane.showInputDialog(Component parentComponent, Object message);
// Example implementation:
String retString = JOptionPane.showInputDialog(this,"Enter your name:");
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in Android you can't really do fully blocking Dialogs, imagine what should happen if there is an incoming phone-call :?:

showAlert, will not help us, as it is a non-blocking dialog. Remember:

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showAlert("A funny title", "MessageBoxes rule extremely!", "Hit Me!", false);
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But there is a pretty easy workaround for doing so...

0. Lets quickly define the Strings we are going to use

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<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="main_app_name">MainActivity - anddev.org</string>
    <string name="main_cmd_opensub">Open SubActivity</string>
    <string name="sub_app_name">SubActivity returning Result - anddev.org</string>
    <string name="subactivity_cmd_return">Return to MainActivity</string>
</resources>
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1. What we need to do is the follwoing:

Override the onActivityResult(...)-method coming from Activity to react on a Activity we opened, that returned sth. .
Start that Activity that will return sth. to us, using: startSubActivity(...)
Call setResult(int resultCode, String data) within our (sub)Activity and close it.

The onActivityResult(...)-method in our MainActivity will be called :!:

2. So this is the layout-file of the MainActivity (we simply need a button, nothing more):
We need to add the id-attribute to the Button, because we need to add an OnClickListener to it.

For basic information about XML-Layouting, take a look :arrow: here.

"/res/layout/main.xml"

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
>
        <Button  id="@+id/mainactivity_cmd_opensub"
                android:layout_width="fill_parent" 
                android:layout_height="wrap_content" 
                android:text="@string/main_cmd_opensub"
    />
</LinearLayout>
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"/src/your_package_structure/MainActivity.java"

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package org.anddev.android.subactivitywithresult;
 
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
 
public class MainActivity extends Activity {
    protected static final int SUB_ACTIVITY_REQUEST_CODE = 1337;
 
        /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        // Apply our main.xml-Layout
        setContentView(R.layout.main);
        
        // Find the button defined in the main.xml
        Button cmd_opensub = (Button)findViewById(R.id.mainactivity_cmd_opensub);
        // Add an OnClickListener to it, that will open the SubActivity
        cmd_opensub.setOnClickListener(new OnClickListener(){
                        // @Override
                        public void onClick(View arg0) {
                                Intent i = new Intent(MainActivity.this, 
                                                                        SubActivityWithResult.class);
                                // We use SUB_ACTIVITY_REQUEST_CODE as an 'identifier'
                                startSubActivity(i, SUB_ACTIVITY_REQUEST_CODE);
                        }
        });        
    }
    
        @Override
        protected void onActivityResult(int requestCode, int resultCode, 
                                                                String data, Bundle extras) {
                super.onActivityResult(requestCode, resultCode, data, extras);
                // Here We identify the subActivity we starte 
                if(requestCode == SUB_ACTIVITY_REQUEST_CODE){
                        // And show its result
                        showAlert("SubActivity returned", "ReturnValue: " + data, 
                                                        "OK", false);
                }
        }
}
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3.Now lets take a look at the SubActivity.xml (provides an EditText to enter the return-String and a "Return to Main"-Button and the SubActivityWithResult-Class, which is also well commented:

"/res/layout/subactivity.xml"

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<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <EditText id="@+id/subactivity_edit_returnvalue" 
         android:layout_width="fill_parent" 
         android:layout_height="wrap_content" 
         android:background="@android:drawable/editbox_background"
         android:singleLine="true"
    />
        <Button id="@+id/subactivity_cmd_return"
            android:layout_width="fill_parent" 
            android:layout_height="wrap_content" 
            android:text="@string/subactivity_cmd_return"
    />
</LinearLayout>
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"/src/your_package_structure/SubActivityWithResult.java"

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package org.anddev.android.subactivitywithresult;
 
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
 
 
public class SubActivityWithResult extends Activity{
        
        protected final int SUCCESS_RETURN_CODE = 1;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
     // Apply our subactivity.xml-Layout
        setContentView(R.layout.subactivity);
        
        // Find the button defined in the subactivity.xml
        Button cmd_return = (Button)findViewById(R.id.subactivity_cmd_return);
        /* Add an OnClickListener to it, that will
         * read out the text in the EditBox set it 
         * as retrn-data and close this activity */
        cmd_return.setOnClickListener(new OnClickListener(){
                        // @Override
                        public void onClick(View arg0) {
                                // Find the edittext defined in the subactivity.xml
                                EditText edit_returvalue = (EditText)findViewById(
                                                R.id.subactivity_edit_returnvalue);
                                SubActivityWithResult.this.setResult(SUCCESS_RETURN_CODE, 
                                                edit_returvalue.getText().toString());
                                // Close this Activity
                                SubActivityWithResult.this.finish();
                        }
        });       
    }
}
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4. And finally the AndroidManifets.xml which was has to be altered like the following:

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<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.anddev.android.subactivitywithresult">
    <application android:icon="@drawable/icon">
        <activity class=".MainActivity" android:label="@string/main_app_name">
            <intent-filter>
                <action android:value="android.intent.action.MAIN" />
                <category android:value="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity class=".SubActivityWithResult" android:label="@string/sub_app_name">
            <intent-filter>
                <action android:value="android.intent.action.VIEW" />
                <category android:value="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
    </application>
</manifest> 
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Thats it, you can easily transform this into a generic InputBox, or just use it somewhere it fits.

Regards,
plusminus

Nitinkcv · by **Nitinkcv** » Mon Dec 03, 2007 10:03 am

Hi,

My query goes something like this.
1)
My first screen contains the textbox and the button. Next i input some code into the textbox and click on the button.
It opens up another activity which actually displays or shows an alert of whatever i had inputted in my first screen(activity)

2)
Also i require to send back an array of strings back to the calling intent. But the current method only allows me to send a string param.

Thanks,
Nitin

plusminus · by **plusminus** » Mon Dec 03, 2007 3:43 pm

Hey Nitinkcv,

the setResult(..) got another Overload, with a Bundle (what is just like a pimped HashMap):

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Activity.setResult(int, java.lang.String, android.os.Bundle);
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The Bundle you had filled somewhere in the SubActivity from above gets passed to the onActivityResult(...)-method of the calling Activity:

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protected void onActivityResult(int requestCode, int resultCode,
                String data, Bundle extras)
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You can easily put/get various Types to a Bundle, even StringArrays:

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Bundle.putStringArray(java.lang.String, java.lang.String[])
Bundle.getStringArray(java.lang.String)
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See Googles JavaDoc for Bundle: android.os.Bundle

Regards,
plusminus

Nitinkcv · by **Nitinkcv** » Mon Dec 03, 2007 6:42 pm

Hi,

How silly of me.. i should have searched for the overloaded methods. thanks a lot.

Right now i have a main class(main.java) which extends activity and another class(sub.java) which extends
ListActivity. I pass a value from my main.java to the sub.java by using the Intent along with Bundle class.
Now in my sub.java based on the value passed i populate a listview:

one of the methods in the sub.java having the problem:

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protected void SearchForText(String searchText){
        
        for (Iterator iterator = codeEntries.iterator(); iterator.hasNext();) {
                        String type = (String) iterator.next();
                        if(type.contains(searchText)){
                                searchEntries.add(searchText);
                        }
                }
        ArrayAdapter<String> SearchList = new ArrayAdapter<String>(this,
                R.layout.filesearchlayout, this.searchEntries);
      
        this.setListAdapter(SearchList);
    }
 
/*where*/
    private List<String> codeEntries = new ArrayList<String>();
    private List<String> searchEntries = new ArrayList<String>();
    
 
 
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However on running the app i find that an classcastexception in thrown in the sub.java.
i debugged and everthing seemed ok till the line where searchList was being assigned. All the search entries were getting populated in the List searchEntries.

But after the line this.setListAdapter(SearchList), on hitting F6 it went into some source files and then the ClassCastException was being hit.

What could be the reason?

is it because the Intent is served from the Activity class while its in the ListView that the Intent is received.

Also do we ALWAYS have to override the method onActivityResult in the class where StartSubActivity is called?

Thanks,
Nitin

plusminus · by **plusminus** » Mon Dec 03, 2007 8:46 pm

Hey Nitinkcv,

most of the time the solution is just one click away, or we just look right over it. I know what i'm talking about ... :roll:

Nitinkcv wrote:Hi,
...
But after the line this.setListAdapter(SearchList), on hitting F6 it went into some source files and then the ClassCastException was being hit.

Hm, that is strange... :!:

Is the Exception thrown at or after the line you said :?:

I tried it with me and it works fine. Which of the parameters does the ClassCastException refer to :?:

as it cannot be this.searchEntries (by logical thinking and its type). The others look also very right:!:

Nitinkcv wrote:What could be the reason? Sad is it because the Intent is served from the Activity class while its in the ListView that the Intent is received.

Don't think that it happens because of the Intent as it only starts your Activity (???) and thats it. But if it was so, there would probably be no ClassCastException...

Nitinkcv wrote:Also do we ALWAYS have to override the method onActivityResult in the class where StartSubActivity is called?

No you don't have to as there is sth. like a default-procedure in the onActivityResult(..) from the Baseclass: Activity we are overriding.

Regards,
plusminus

Nitinkcv · by **Nitinkcv** » Tue Dec 04, 2007 2:38 pm

A trivial mistake. i had given the layout file which is being used by my main.java.
this had the relative layout

just had another query. is it possible for me to retain a layout having a textbox and then a list of items.
what i mean is that my sub.java which extends the listactivity would have a textbox at the top plus the list of all the search entries?

Similar to the sorts of MasterPages in .Net 2.0

Thanks,
Nitin

plusminus · by **plusminus** » Tue Dec 04, 2007 3:52 pm

Hello Nitincv,

yes it it possible, like it is even possible, to have a EditText, a MapView and Buttons in one layout :!:

:arrow: Have a look here.

Regards,
plusminus

Nitinkcv · by **Nitinkcv** » Tue Dec 04, 2007 4:43 pm

Hi,

Would be eagerly waiting to get my hands on the source code of that map app.

Thanks,
Nitin

plusminus · by **plusminus** » Tue Dec 04, 2007 4:54 pm

Hi Nitinkcv,

I have nothing received so far. Will post it there immediately if lordhong finished cleaning up the code

Regards,
plusminus

venkat · by **venkat** » Wed Dec 12, 2007 6:10 pm

i run above program and when i press the "Open Sub Activity" button it will show Error message:(. i have attached error screen shot. i can't fix that error. can u any one help me to solve this problem.

regads,
venkat.

plusminus · by **plusminus** » Wed Dec 12, 2007 6:43 pm

Hello venkat,

read closely between the lines, there it says: "plusminus forgot to append the altered AndroisManifest.xml :!:

"

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<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.anddev.android.subactivitywithresult">
    <application android:icon="@drawable/icon">
        <activity class=".MainActivity" android:label="@string/main_app_name">
            <intent-filter>
                <action android:value="android.intent.action.MAIN" />
                <category android:value="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity class=".SubActivityWithResult" android:label="@string/sub_app_name">
            <intent-filter>
                <action android:value="android.intent.action.VIEW" />
                <category android:value="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
    </application>
</manifest> 
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Appended it above too.

Regards,
plusminus

venkat · by **venkat** » Thu Dec 13, 2007 7:21 am

Thank you very much Plusminus :wink:

bloonlabs · by **bloonlabs** » Sun Jan 20, 2008 10:55 pm

Ok so I was working on my seperate class today for my app and I keep on coming to the same problem. When I finish the subActivity it just closes the entire program. According to my code it should go back to my main class which will then do stuff. Here is my code:

The subActivity finish():

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        Button b_save = (Button) findViewById(R.id.b_save);
 
        b_save.setOnClickListener(new Button.OnClickListener() {
 
            public void onClick(View v) {
 
                editor.commit();
 
                Options.this.setResult(RESULT_OK); 
 
                Options.this.finish();
 
            }
 
        });
 
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The main class:

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    @Override
 
    protected void onActivityResult(int requestCode, int resultCode, String data, Bundle extras) {
 
        super.onActivityResult(requestCode, resultCode, data, extras);
 
        if (requestCode == ACTIVITY_OPTIONS) {
 
                if (resultCode == RESULT_OK) restartWilfred();
 
                else if (resultCode == RESULT_CANCELED) gotoMainScreen();
 
        }
 
    }
 
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More code can be found at the svn: http://projectwilfred.googlecode.com/svn/

Thanks!!

plusminus · by **plusminus** » Sun Jan 20, 2008 11:40 pm

Hello bloonlabs,

the debugger never reaches the onActivityResult(...) :?:

Try to ensure such stuff with some logging ( Log.d(...) ).

Thats pretty strange...

Your code looks right :!:

, but the error has to hide somewhere.
Perhaps you used some IDs that should not be used.

Try the ID-Values from this tutorial, because they did work with me.

You could try to run exactly the same code from the tutorial, because I can ensure that it works. If it doesn't your problem is perhaps a problem of the emulator.

Regards,
plusminus

venkat · by **venkat** » Mon Feb 04, 2008 12:27 pm

Hi plus minus,
Above code is very help full to me. now, I have a problem.
Can you tell me , how to pass value from "activity" to "sub Activity"? (or)
can you tell me how to declare global veriable?

SubActivites with return value - The InputBox

SubActivites with return value - The InputBox

Can we do it the other way round

ClassCastException!!

Re: ClassCastException!!

ClassCastException

Source code for Link.

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