Loading New Data with Back Button?

android.developer27 · by **android.developer27** » Sat Apr 11, 2009 4:14 pm

I have a message application so that on view 1 is displayed a list of messages and when you go to view 2 (subactivity) you can send a message. I want the program to work so that when you hit the android back button, you can go back to view 1 and see the list of messages including the new message. Right now only the old data is displayed, and I noticed that displayContent() is not called when going back which I assumed it would. Is there any way to specify that when the back button is hit, to call displayContent() again on the previous activity?

padde · by **padde** » Sun Apr 12, 2009 11:40 pm

Here an working example...

Main Activity

Syntax: [ Download ] [ Hide ]

Using java Syntax Highlighting

 
package de.test;
 
import java.util.Vector;
 
import android.app.ListActivity;
 
import android.content.Context;
 
import android.content.Intent;
 
import android.os.Bundle;
 
import android.os.Handler;
 
import android.os.Message;
 
import android.view.View;
 
import android.view.ViewGroup;
 
import android.widget.BaseAdapter;
 
import android.widget.Button;
 
import android.widget.ListView;
 
import android.widget.TextView;
 
import de.test.sub.SubActivity;
 
public class Test extends ListActivity {
 
    private TestAdapter myAdapter;
 
    private ListView myListView;
 
    public static MyHandler handler;
 
    public void onCreate(Bundle savedInstanceState) {
 
        super.onCreate(savedInstanceState);
 
        myListView = getListView();
 
        handler = new MyHandler();
 
        Button addButton = new Button(this);
 
        addButton.setText("Add Item");
 
        addButton.setOnClickListener(new Button.OnClickListener() {
 
            public void onClick(View v) {
 
                startActivity(new Intent(Test.this, SubActivity.class));
 
            }
 
        });
 
        myListView.addHeaderView(addButton);
 
        myAdapter = new TestAdapter(this);
 
        setListAdapter(myAdapter);
 
        myAdapter.addItem("not much");
 
    }
 
    public class MyHandler extends Handler {
 
        public void handleMessage(Message msg) {
 
            if(msg.what == 1) {
 
                myAdapter.addItem((String) msg.obj);
 
            }
 
            super.handleMessage(msg);
 
        }
 
    }    
 
    private class TestAdapter extends BaseAdapter {
 
        private Context cntxt;
 
        private Vector<String> items;
 
        public TestAdapter(Context context) {
 
            cntxt = context;
 
            items = new Vector<String>(); 
 
        }
 
        public void addItem(String item){ 
 
            items.add(item); 
 
            notifyDataSetChanged(); 
 
        }
 
        public int getCount() { return items.size(); }
 
        public Object getItem(int position) { return items.get(position); }
 
        public long getItemId(int position) { return position; }
 
        public View getView(int position, View convertView, ViewGroup parent) {
 
            TextView tv;
 
            if (convertView == null) 
 
                tv = new TextView(cntxt); 
 
            else 
 
                tv = (TextView)convertView;
 
            tv.setText(items.get(position));
 
            return tv;
 
        }
 
    }
 
}
 
Parsed in 0.041 seconds,  using GeSHi 1.0.8.4

Sub Activity

Syntax: [ Download ] [ Hide ]

Using java Syntax Highlighting

 
package de.test.sub;
 
import android.app.Activity;
 
import android.os.Bundle;
 
import android.os.Message;
 
import android.widget.EditText;
 
import android.widget.LinearLayout;
 
import android.widget.LinearLayout.LayoutParams;
 
import de.test.Test;
 
public class SubActivity extends Activity {
 
    private EditText et;
 
    public void onCreate(Bundle savedInstanceState) {
 
        super.onCreate(savedInstanceState);
 
        LinearLayout lin = new LinearLayout(this);
 
        LayoutParams param = new LayoutParams(-1,-2);
 
        lin.setLayoutParams(param);
 
        et = new EditText(this);
 
        et.setSingleLine();
 
        et.setLayoutParams(param);
 
        lin.addView(et);
 
        setContentView(lin);
 
    }
 
    protected void onPause() {
 
        super.onPause();
 
        Message msg = Test.handler.obtainMessage();
 
        msg.what = 1;
 
        msg.obj = et.getText().toString();
 
        Test.handler.sendMessage(msg);
 
        finish();
 
    }
 
}
 
Parsed in 0.034 seconds,  using GeSHi 1.0.8.4

When the SubActivity is visible and you press the back button on the device/emulator onPause is called
where a message is generated with the current content of the edittext afterwards the message get send
to the messagehandler of the main activity.

Greets
Padde

Loading New Data with Back Button?

Loading New Data with Back Button?

Who is online