state added

Author: maciej-nowak

state/README.md

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+# state
+This is repository of http://androidcode.pl blog. It shows uses of State pattern in Android. It is a part of Design Patterns - State post in the blog. 

state/example/Main.java

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+public class Main {
+	
+	public static vodi main() {
+		//user create playlist
+		List<Track> playlist = new ArrayList<>();
+		playlist.add(new Track("Depeche Mode", "Enjoy the silence", 250, "dm01.mp3"));
+		playlist.add(new Track("Abba", "Dancing Queen", 195, "abba07.mp3"));
+		playlist.add(new Track("Ben Howard", "Keep your head up", 217, "bh04.mp3"));
+		playlist.add(new Track("Of Monsters and Men", "Yellow Light", 184, "omm12.mp3"));
+
+		//user choose playlist to play right now
+		Player player = new Player(playlist);
+
+		//player is initialized and ready to play the first song
+		player.play(); //Enjoy the silence is playing (StopState)
+		player.next(); //Dancing Queen is playing (PlayState)
+		player.stop(); //Dancig Queen is pausing (StopState)
+		player.previous(); //Enjoy the sielence is loaded again (StopState)
+		player.play(); //Enjoy the silence is playing (PlayState)
+		player.previous(); //Enojy the sielence is playing from the beginning (PlayState)
+	}
+}

state/example/Player.java

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+public class Player {
+
+    private State state;
+    private List<Track> tracks;
+    private int currentTrack;
+    //other fields like system or music controllers
+
+    public Player(List<Track> tracks){
+        this.tracks = tracks;
+        currentTrack = 0;
+        currentTime = 0;
+        state = new StopState();
+    }
+
+    public void setState(State state){
+        this.state = state;
+    }
+
+    public State getState(){
+        return state;
+    }
+
+    public void play() {
+        state.play(this);
+    }
+
+    public void next() {
+        state.next(this);
+    }
+
+    public void previous() {
+        state.previous(this);
+    }
+
+    public void playTrack() {
+        //play the currentTrack
+        //change UI button
+    }
+
+    public void stopTrack() {
+        //stop the currentTrack
+        //change UI button
+    }
+
+    public void nextTrack() {
+        //stop the CurrentTrack
+        if(currentTrack < tracks.size() - 1)
+            currentTrack++;
+        else
+            currentTrack = 0;
+        //play the currentTrack
+        //change UI info
+    }
+
+    public void previousTrack() {
+        if(currentTrack > 0)
+            currentTrack = tracks.size() - 1;
+        else
+            currentTrack--;
+        //play the currentTrack
+        //change UI info
+    }
+}

state/example/dummy/Track.java

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+public class Track {
+	
+	private String author;
+	private String title;
+	private int lengthSeconds;
+	private String fileName;
+
+	public Track(String author, String title, int lengthSeconds, String fileName) {
+		this.author = author;
+		this.title = title;
+		this.lengthSeconds = lengthSeconds;
+		this.fileName = fileName;
+	}
+
+	//setter, getter and other methods
+}

state/example/states/PlayState.java

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+public class PlayState implements State {
+
+    //do some things in every methods and run player's method or modify player if needed
+
+    @Override
+    public void play(Player player) {
+        player.stopTrack();
+        player.setState(new StopState());
+    }
+
+    @Override
+    public void next(Player player) {
+        player.nextTrack();
+    }
+
+    @Override
+    public void previous(Player player) {
+        player.playTrack();
+    }
+}

state/example/states/State.java

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+interface State {
+
+    void play(Player player);
+    void next(Player player);
+    void previous(Player player);
+}

state/example/states/StopState.java

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+public class StopState implements State {
+
+    //do some things in every methods and run player's method or modify player if needed
+
+    @Override
+    public void play(Player player) {
+        player.playTrack();
+        player.setState(new PlayState());
+    }
+
+    @Override
+    public void next(Player player) {
+        player.nextTrack();
+    }
+
+    @Override
+    public void previous(Player player) {
+        player.previousTrack();
+    }
+}

state/pattern/Context.java

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+public class Context {
+
+    private State state;
+
+    public Context() {
+        //set default state
+        state = new State1(this);
+    }
+
+    public void request() {
+        state.handle(this);
+    }
+
+    public void action1() {
+        //do something specific for action1
+    }
+
+    public void action2(boolean enabled) {
+        //do something specific for action2
+    }
+
+    public void setState(State state) {
+        this.state = state;
+    }
+
+    public State getState() {
+        return state;
+    }
+}

state/pattern/Main.java

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+public class Main {
+	
+	public static void main() {
+		//start state is State1
+		Context context = new Context();
+
+		//user request operation
+		context.request(); //State1 handle the action
+		//operation is done, state has changed
+
+		//user again request operation many times during the state is changing
+		context.request(); //State2 handle the action
+		context.request(); //State3 handle the action
+		context.request(); //again State1 handle the action
+	}
+}

state/pattern/states/State.java

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+interface State {
+
+    void handle(Context context);
+}