Task e gestione del Back Stack
- Nota: il back stack non viene mai riarrangiato, su di esso vengono effettuate esclusivamente operazioni di push() e pop()
<?xml version="1.0" encoding="utf-8"?><manifest package="it.alcacoop.backgammon"><uses-sdk android:minSdkVersion="5"android:targetSdkVersion="17" /><application><activity></activity></application></manifest>
android create project \--target <target_ID> \--name <your_project_name> \--path path/to/your/project \--activity <your_activity_name> \--package <your_package_namespace>
AndroidManifest.xml
bin
gen
proguard.cfg
project.properties
res
src
drawable-hdpi
drawable-ldpi
drawable-mdpi
layout
raw
values
<uses-permissionandroid:name="android.permission.INTERNET"/><uses-permissionandroid:name="android.permission.ACCESS_NETWORK_STATE"/>
private boolean isNetworkAvailable() {ConnectivityManager connectivityManager =getSystemService(Context.CONNECTIVITY_SERVICE);NetworkInfo activeNetworkInfo =connectivityManager.getActiveNetworkInfo();return activeNetworkInfo != null;}
Android fornisce un robusto modello di sicurezza, caratterizzato da diversi livelli di implementazione e granularità a livello applicativo
<application><activity android:name=".ExampleActivity"/><activity android:name=".ExampleActivity2"/>...</application
<intent-filter><action android:name="android.intent.action.MAIN"/><category android:name="android.intent.category.LAUNCHER"/></intent-filter>
| Activity Lifecycle Methods | |||
|---|---|---|---|
| Method | Description | Killable | Next |
| onCreate() | Called when activity first created | No | onStart() |
| onRestart() | Called after activity stopped, prior to restarting | No | onStart() |
| onStart() | Called when activity is becoming visible to user | No | onResume()/onStop() |
| onResume() | Called when activity starts interacting with user | No | onPause() |
| onPause() | Called when a previous activity is about to resume | Yes | onResume()/onStop() |
| onStop() | Called when activity no longer visible to user | Yes | onRestart()/onDestroy() |
| onDestroy() | Final call received before activity is destroyed | Yes | Nothing |
Reimplementiamo tutti gli hook che gestiscono il ciclo di vita di una activity con delle semplici print (Log.*)...
@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);Log.e("LIFECYCLE", "CREATE!!!");}@Overridepublic void onRestart() {super.onRestart();Log.e("LIFECYCLE", "RESTART!!!");}...
adb shell #apre una shell sul dispositivops #mostra la lista dei processi attivi
public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);}
<Buttonandroid:id="@+id/create_dialog"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Open Dialog!" />
Nota: è sempre necessario assegnare un ID ai compenenti che si aggiungono, attraverso il quale sarà possibile referenziare l'oggetto nel codice Java
final Button button =(Button) findViewById(R.id.create_dialog);button.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {//DO SOMETHING}});
private AlertDialog dialog;public void createDialog() {AlertDialog.Builder builder =new AlertDialog.Builder(this);builder.setMessage("HELLO!").setTitle("TEST DIALOG").setPositiveButton("OK", null);dialog = builder.create();}
onCreate() {setContentView...createDialog...button.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {dialog.show();}});}
Layout:
<TextViewandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:text="@string/hello_world"
string.xml
<resources><string name="hello_world">Hello World from MainActivity</string></resources>
Accedere programmaticamente ad una stringa:
(String)getResources().getText(R.string.hello_world)/** Creazione di una Intent esplicita** param Context Application Context* param Class Component Class*/Intent myIntent = new Intent(this, MainActivity.class);
Intent myIntent = new Intent(Intent.ACTION_VIEW,Uri.parse("http://google.it"));
<intent-filter><action android:name="android.intent.action.MAIN"/><category android:name="android.intent.category.LAUNCHER"/></intent-filter>
<intent-filter><action android:name="android.intent.action.VIEW"/><category android:name="android.intent.category.DEFAULT"/><category android:name="android.intent.category.BROWSABLE"/><data android:scheme="http"/><data android:scheme="https"/><data android:host="youtube.com"/><data android:host="www.youtube.com"/><data android:host="m.youtube.com"/><data android:pathPrefix="/watch"/><data android:pathPrefix="/v/"/><data android:pathPrefix="/e/"/><data android:pathPrefix="/embed/"/></intent-filter>
<Buttonandroid:id="@+id/open_google"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Send Intent!"android:onClick="sendIntent"/>
public void sendIntent(View view) {Intent myIntent = new Intent(Intent.ACTION_VIEW,Uri.parse("http://google.it"));startActivity(myIntent);}
class MyThread extends Thread {public void run() {//LOGICA DI ESECUZIONE}}MyThread myThread = new MyThread();myThread.start(); //LANCIA IL THREAD
Thread(Runnable r)class MyRunnable implements Runnable {public void run() {//LOGICA DI ESECUZIONE}}MyRunnable r = new MyRunnable();Thread myThread = new Thread(r);myThread.start(); //LANCIA IL THREAD
//LONG TASKpublic void longTask() {File root = Environment.getExternalStorageDirectory();File file = new File(root, "test.txt");try {if (root.canWrite()){FileWriter filewriter = new FileWriter(file);BufferedWriter out = new BufferedWriter(filewriter);for (int i=0; i<1000000; i++) out.write(i);out.close();}} catch (IOException e) {}}
button.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {longTask();dialog.show();}});
public void onClick(View v) {Thread t = new Thread() {@Overridepublic void run() {longTask();dialog.show();}};t.start();}
public void onClick(View v) {Thread t = new Thread() {@Overridepublic void run() {longTask();runOnUiThread(new Runnable() {@Overridepublic void run() {dialog.show();}});}};t.start();}