#Building a basic discussion forum app

Dev Environment

Download and install android studio and android SDK

Getting Started

1. Open android studio, click start new project.
2. Set minimum target API to 4.0.3 (API 15)
3. Choose Blank Activity

Setting up views

Main View

1. Declare some class properties in MainActivity

    private ListView listView;
    private ArrayAdapter<String> adapter;
    private ArrayList<String> arrayList;
   

2. Add a mock list to onCreate in MainActivity

    listView = (ListView) findViewById(R.id.listView);
    arrayList = new ArrayList<String>();
    arrayList.add("thread1");
    arrayList.add("thread2");
    arrayList.add("thread3");
    arrayList.add("thread4");
    adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, arrayList);
    listView.setAdapter(adapter);
   

3. Make a add item to list function

    public void addItem(String text) {
    	arrayList.add(text);
    	adapter.notifyDataSetChanged();
    }
   

Thread View

1. Create new activity Thread, add behaviour to ListView in MainActivity:

    listView.setOnItemClickListener(new OnItemClickListener() {
    	@Override
    	public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    		String threadId = (String) parent.getItemAtPosition(position);
    		Intent intent = new Intent(MainActivity.this, Thread.class);
    		intent.putExtra(threadId, threadId);
    		startActivity(intent);
    	}
    });
   

2. In Thread class, add to onCreate function:

    Intent intent = getIntent();
    String threadId = intent.getStringExtra(Thread.threadId);
    TextView threadTitle = (TextView) findViewById(R.id.textView);
    getSupportActionBar().setTitle("Thread");
    threadTitle.setText("Mock thread title");
   

New Thread view

1. In res > values > strings, add <string name="action_new_thread">New Thread</string>

2. In res > menu > menu_main.xml, add <item android:id="@+id/action_new_thread" android:title="@string/action_new_thread" android:orderInCategory="100" app:showAsAction="never" />

3. In MainActivity class, modify onOptionsItemSelected to this:

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
    	int id = item.getItemId();
    	if (id == R.id.action_new_thread) {
    			return true;
    	}
    	return super.onOptionsItemSelected(item);
    }
   

Integrating Parse (Prebuilt backend)

Source: https://parse.com/apps/quickstart#parse_data/mobile/android/native/existing

1. Download parse SDK from https://parse.com/apps/quickstart#parse_data/mobile/android/native/existing

2. Drag the Parse-*.jar you downloaded into your existing app's "libs" folder and add the following to your build.gradle

3. Add to app module build.gradle:

    dependencies {
    	compile 'com.parse.bolts:bolts-android:1.+'
    	compile fileTree(dir: 'libs', include: 'Parse-*.jar')
    }
   

4. Add to onCreate method in mainActivity:

    Parse.enableLocalDatastore(this);
    Parse.initialize(this, "dbSRgndFtVlkxJUG1AcubhVaP814yfO0HAqrEjaU", "LWqPDlBCoLfhG2bG7ZvjKdNpvcbl8JARkLHcaoWf");
    populateMessages();
   

5. populateMessages method:

    public void populateMessages() {
    	ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("Thread");
    	query.findInBackground(new FindCallback<ParseObject>() {
    		public void done(List<ParseObject> messages, ParseException e) {
    			for (ParseObject message: messages) {
    				addItem(message.getString("title"));
    			}
    		}
    	});
    }
   

6. Add to manifest file:

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

This method is NOT good it makes parse avaliable to only one activity. For any serious app building, MVC is needed.

Next steps

Switching default listviews for custom listviews

Putting parse on a service (MVC)

Extra features

Switching default listviews for custom listviews

The default listviews in android are not customizable. For any serious app, it is important to implement custom listviews.

Step 1

Add RecyclerView library to app gradle compile 'com.android.support:recyclerview-v7:+'

Step 2

Define your data class:

class Post {
	private String mTitle, mContent;

	public Post(String title, String content) {
		mTitle = title;
		mContent = content;
	}

	public String getContent() {
		return mContent;
	}

	public void setContent(String content) {
		mContent = content;
	}

	public String getTitle() {
		return mTitle;
	}

	public void setTitle(String title) {
		mTitle = title;
	}
}

Initialize your data in your activity:

	protected void onCreate(Bundle savedInstanceState) {
		...

		ArrayList<Post> posts = new ArrayList<>();
		posts.add(new Post("some title", "some content"));
		posts.add(new Post("some title 2", "some content 2"));
		posts.add(new Post("some title 3", "some content 3"));
		posts.add(new Post("some title 4", "some content 4"));
	}

Define your item view (layouts/post.xml):

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
							xmlns:tools="http://schemas.android.com/tools"
							android:layout_width="match_parent"
							android:layout_height="match_parent"
							android:layout_marginBottom="8dp"
							android:layout_marginTop="8dp"
							android:orientation="vertical">

	<TextView
		android:id="@+id/title"
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
		android:textSize="20sp"
		tools:text="Title"/>

	<TextView
		android:id="@+id/content"
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
		tools:text="Content"/>
</LinearLayout>

Step 3

Create an adapter:

public class PostListAdapter extends RecyclerView.Adapter<PostListAdapter.PostViewHolder> {

	private List<Post> mPosts;

	public PostListAdapter(List<Post> posts) {
		mPosts = posts;
	}

	@Override
	public PostViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
		View view  = LayoutInflater.from(parent.getContext()).inflate(R.layout.post, parent, false);
		PostViewHolder viewHolder = new PostViewHolder(view);
		return viewHolder;
	}

	@Override
	public void onBindViewHolder(PostViewHolder holder, int position) {
		Post post = mPosts.get(position);
		holder.bind(post);
	}

	@Override
	public int getItemCount() {
		return mPosts.size();
	}

	public class PostViewHolder extends RecyclerView.ViewHolder {
		private TextView mTitle, mContent;
		private Post mPost;

		public PostViewHolder(final View itemView) {
				super(itemView);
				mTitle = (TextView) itemView.findViewById(R.id.title);
				mContent = (TextView) itemView.findViewById(R.id.content);
				itemView.setOnClickListener(new View.OnClickListener() {
						@Override
						public void onClick(View v) {
								Toast.makeText(itemView.getContext(), "You clicked '" + mPost.getTitle() + "'", Toast.LENGTH_SHORT).show();
						}
				});
		}

		public void bind(Post post) {
				mPost = post;
				mTitle.setText(post.getTitle());
				mContent.setText(post.getContent());
		}
	}
}

Step 4

Add RecyclerView to layout

<android.support.v7.widget.RecyclerView
		android:layout_width="match_parent"
		android:layout_height="wrap_content"
		android:id="@+id/recycler_view"/>

Set it up in your activity

	onCreate() {
		...
		RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
		recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
		recyclerView.setAdapter(new PostListAdapter(posts));
	}

Sample Project

By Daniel Rampelt
https://drive.google.com/file/d/0BzW6GHHHAXgIS2tydEJNX20xZzA/view?usp=sharing