MobileDevelopment

Introduction This note will be used to keep track of all the knowledge gained during Android development

Development Component

Service

Step 1: Create Service class whihc extends Service

Instruction

Step 2: Start & stop service

普通的Service的生命周期很简单，分别为onCreate、onStartCommand、onDestroy这三个。当我们startService()的时候，首次创建Service会回调onCreate()方法，然后回调onStartCommand()方法，再次startService()的时候，就只会执行onStartCommand()。服务一旦开启后，我们就需要通过stopService()方法或者stopSelf()方法关闭服务，这时就会回调onDestroy()

MainActivity.class 

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// start
Intent sIntent = new Intent(this, Myservice.class)
startService(sIntent)

// stop
stopService(sIntent)

MyService.class

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// startService would invoke onStartCommand method in MyService class
// In general, this method would create sub-thread to running service
public int onStartCommand(Intent intent, int flags, int startId) {
	Runnable runnable = new Runnable() {
	@Override
	public void run() {
		Log.i(TAG, "generate random number running");
		}
	};
	Thread thread = new Thread(runnable);
	// execute linearly not multi-thread, would stoke program
	// thread.run();
	// achieve multi-thread
	thread.start();
	/*
	START_STICKY: automatically restart after being killed and calls onStartCommand again, it can accept the new task instead of continuing with the previous task
	START_NOT_STICKY: Do not restart after being killed, do not keep the startup state, can stop at any time
	START_REDELIVER_INTENT: If there is an unfinished Intent, it is restarted after being killed, and all intents are sent after the restart. After stopSelf releases the maintained Intent.
	*/
	return START_NOT_STICKY;
}


// stopService
public void onDestroy() {
	super.onDestroy();
}

Step 3: Bind & Unbind service

MainActivity.class 

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// bind
private void bindMyService() {
	if (myServiceConnection == null) {
		myServiceConnection = new ServiceConnection() {
		@Override
		public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
			Log.i(TAG, "onServiceConnected");
			MyService.MyBinder binder = (MyService.MyBinder) iBinder;			myService = ((MyService.MyBinder) iBinder).getService();                 
		}

		@Override
		public void onServiceDisconnected(ComponentName componentName) {
			Log.i(TAG, "onServiceDisconnected");
		}
		};
	}

	// Intent, new Service Connection
	// BIND_AUTO_CREATE: check if there are connections before stoping services

	bindService(sIntent, myServiceConnection, BIND_AUTO_CREATE);
}

// unbind
private void unbindMyService() {
	unbindService(myServiceConnection);
	myServiceConnection = null;
}

MyService.class

bind
Define Binder class

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public class MyBinder extends Binder {
        public MyService getService() {
            return MyService.this;
        }
}

Define MyBinder instance

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private Binder myBinder = new MyBinder();

Define onBind Method return binder

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@Override
// you can get this binder in creating serviceConnection in MainActivity.class
public IBinder onBind(Intent intent) {
	return myBinder;
}

Unbind

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@Override
public void unbindService(ServiceConnection conn) {
	super.unbindService(conn);
}

Demo

ListView

Define Item in the listview

define attribute of every row

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public class Item {
    private String name;
    private int img_url;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Item(String name) {
        this.name = name;
    }
    
    public int getImg_url() {
        return img_url;
    }
    
    public void setImg_url(int img_url) {
        this.img_url = img_url;
    }

}

Define xml in each item

show in each row

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<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/item_image"
        android:layout_width="130dp"
        android:layout_height="130dp" />


    <TextView
        android:id="@+id/item_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textStyle="bold"
        android:textColor="#0000EE"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="30dp"
        android:textSize="25sp"
        android:gravity="center"/>


</LinearLayout>

Define Adapter

Connect the background data to the foreground style 

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public class ItemAdapter extends ArrayAdapter<Item> {
    private int resourceId;
    public ItemAdapter(Context context,int textViewResourceId, List<Item> objects){
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Item item = getItem(position);
        View view;
        ViewHolder viewHolder;

        if (convertView == null){
            view = LayoutInflater.from(getContext()).inflate(resourceId, null);

            viewHolder = new ViewHolder();
            viewHolder.itemImage = (ImageView) view.findViewById(R.id.item_image);
            viewHolder.itemName = (TextView) view.findViewById(R.id.item_name);

            view.setTag(viewHolder);
        }else{
            view = convertView;
            viewHolder = (ViewHolder) view.getTag();
        }


        viewHolder.itemImage.setImageResource(item.getImg_url());
        viewHolder.itemName.setText(item.getName());
        return view;
    }

    class ViewHolder{
        ImageView itemImage;
        TextView itemName;
    }

}

MainActivity(Omit definition MainActivity.XML)

set Data and click listener

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...
		// define data source
		List<Item> itemList = new ArrayList<Item>();
		Item alpha = new Item("Alpha",R.drawable.alpha, "https://en.wikipedia.org/wiki/Alpha","API 1");
        itemList.add(alpha);
        
        // add and set adapter
		ItemAdapter adapter = new ItemAdapter(MainActivity.this,R.layout.item, itemList);

       ListView listView = (ListView) findViewById(R.id.list_view);
       listView.setAdapter(adapter);


		// add click listener
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener(){

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                                    int position, long id) {
                // TODO Auto-generated method stub
                Item info = itemList.get(position);
                Bundle bundle = new Bundle();

                bundle.putString("itemName", info.getName());
                bundle.putString("itemImage", info.getImg_url() + "");
                bundle.putString("itemLink", info.getLink());

                Intent intent = new Intent(MainActivity.this,ItemPage.class);
                intent.putExtras(bundle);
                startActivity(intent);
            }
});
...

ToolBar

Hide actionbar to show toolbar

Change theme of this activity in AndroidManifest.xml, and this theme is define in styles.xml 

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// AndroidManifest.xml
      <activity android:name=".activity_name"
          android:theme="@style/AppTheme.NoActionBar"
          ></activity>
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// styles.xml
 <style name="AppTheme.NoActionBar">  
        <item name="windowNoTitle">true</item>  
        <item name="windowActionBar">false</item>  
    </style>

Define XML

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// there is a back button in ToolBar
    <androidx.appcompat.widget.Toolbar
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        android:id="@+id/toolbar"
        android:background="?colorPrimary"
        android:layout_width="fill_parent"
        android:layout_height="?actionBarSize"
        android:minHeight="?actionBarSize"
        app:popupTheme="?actionBarPopupTheme"
        app:navigationIcon="?homeAsUpIndicator"
        xmlns:app="http://schemas.android.com/apk/res-auto" />

MainActivity

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...
		mToolbar = (androidx.appcompat.widget.Toolbar) findViewById(R.id.toolbar);
		// set support to this toolbar
        setSupportActionBar((Toolbar) mToolbar);
        // set click listener
        ((Toolbar) mToolbar).setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                finish();
            }
        });
...

WebView

Define XML

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<WebView
        android:id="@+id/web_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

open permission in AndroidManifest.xml

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

MainActivity

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webView = (WebView) findViewById(R.id.web_view);
      webView.getSettings().setJavaScriptEnabled(true);
      webView.loadUrl(link);
      
      
      // not jump to external browser
      webView.setWebViewClient(new WebViewClient(){
          @Override
          public boolean shouldOverrideUrlLoading(WebView view, String url) {
              view.loadUrl(url);
              return super.shouldOverrideUrlLoading(view, url);
          }
      });

Intent

post 

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// add attribute
Bundle bundle = new Bundle();

            bundle.putString("itemName", info.getName());
            bundle.putString("itemImage", info.getImg_url() + "");
            bundle.putString("itemLink", info.getLink());

            Intent intent = new Intent(MainActivity.this,ItemPage.class);
            // first way post
            // intent.putExtra("itemLink",info.getLink());
            // second way post
            intent.putExtras(bundle);
            startActivity(intent);
            // if finish() cannot back again
            // finish();

get 

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// first way get
// getIntent().getStringExtra("link");
// second way get
 Bundle b=getIntent().getExtras();
      //获取Bundle的信息
      String link = b.getString("itemLink");

Version Problem between AndroidX and android.support.v7.XXX

CSDN Version Control

Android Studio emulator rotate screen(portrait & landsacpe)

Instruction

Demo

Title:MobileDevelopment

Author:

Created:2020-10-21, 08:17:35

Updated:2020-10-28, 16:05:33

Full URL:http://example.com/2020/10/21/MobileDevelopment/

License: "CC BY-NC-SA 4.0" Keep Link & Author if Distribute.

Contents
  1. 1. Development Component
    1. 1.1. Service
      1. 1.1.1. Step 1: Create Service class whihc extends Service
      2. 1.1.2. Step 2: Start & stop service
      3. 1.1.3. Step 3: Bind & Unbind service
    2. 1.2. ListView
      1. 1.2.1. Define Item in the listview
      2. 1.2.2. Define xml in each item
      3. 1.2.3. Define Adapter
      4. 1.2.4. MainActivity(Omit definition MainActivity.XML)
    3. 1.3. ToolBar
      1. 1.3.1. Hide actionbar to show toolbar
      2. 1.3.2. Define XML
      3. 1.3.3. MainActivity
    4. 1.4. WebView
      1. 1.4.1. Define XML
      2. 1.4.2. open permission in AndroidManifest.xml
      3. 1.4.3. MainActivity
    5. 1.5. Intent
    6. 1.6. Version Problem between AndroidX and android.support.v7.XXX
    7. 1.7. Android Studio emulator rotate screen(portrait & landsacpe)
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