This article is reproduced from: http://blog.csdn.net/luoshengyang/article/details/6580267
we are at Android The purpose of adding hardware services to the system is to allow the APP of the application layer to pass Java interface to access hardware services. So, how does the APP access the hardware services provided by the Application Frameworks layer through the Java interface? In this article, we will add a built-in application to the application layer of the Android system. This built-in application obtains the specified service through the ServiceManager interface, and then obtains hardware services through this service.
1. Reference Adding hardware access services to the Application Frameworks layer of the Android system on Ubuntu In this article, define your own hardware service HelloService in the Application Frameworks layer, and provide the IHelloService interface to provide access services.
2. In order to facilitate development, we can use the Android SDK to develop Android applications in the IDE environment. After the development is completed, transplant the program source code to the Android source code project directory. It is very convenient to use Eclipse's Android plug-in ADT to create an Android project, which is not described here. You can refer to other information on the Internet. The project name is Hello, and the main file is as follows:
The main program is src/shy/luo/hello/Hello.java:
1 package shy.luo.hello;
2
3 import shy.luo.hello.R;
4 import android.app.Activity;
5 import android.os.ServiceManager;
6 import android.os.Bundle;
7 import android.os.IHelloService;
8 import android.os.RemoteException;
9 import android.util.Log;
10 import android.view.View;
11 import android.view.View.OnClickListener;
12 import android.widget.Button;
13 import android.widget.EditText;
14
15 public class Hello extends Activity implements OnClickListener {
16 private final static String LOG_TAG = "shy.luo.renju.Hello";
17
18 private IHelloService helloService = null;
19
20 private EditText valueText = null;
21 private Button readButton = null;
22 private Button writeButton = null;
23 private Button clearButton = null;
24
25 /** Called when the activity is first created. */
26 @Override
27 public void onCreate(Bundle savedInstanceState) {
28 super.onCreate(savedInstanceState);
29 setContentView(R.layout.main);
30
31 helloService = IHelloService.Stub.asInterface(
32 ServiceManager.getService("hello"));
33
34 valueText = (EditText)findViewById(R.id.edit_value);
35 readButton = (Button)findViewById(R.id.button_read);
36 writeButton = (Button)findViewById(R.id.button_write);
37 clearButton = (Button)findViewById(R.id.button_clear);
38
39 readButton.setOnClickListener(this);
40 writeButton.setOnClickListener(this);
41 clearButton.setOnClickListener(this);
42
43 Log.i(LOG_TAG, "Hello Activity Created");
44 }
45
46 @Override
47 public void onClick(View v) {
48 if(v.equals(readButton)) {
49 try {
50 int val = helloService.getVal();
51 String text = String.valueOf(val);
52 valueText.setText(text);
53 } catch (RemoteException e) {
54 Log.e(LOG_TAG, "Remote Exception while reading value from device.");
55 }
56 }
57 else if(v.equals(writeButton)) {
58 try {
59 String text = valueText.getText().toString();
60 int val = Integer.parseInt(text);
61 helloService.setVal(val);
62 } catch (RemoteException e) {
63 Log.e(LOG_TAG, "Remote Exception while writing value to device.");
64 }
65 }
66 else if(v.equals(clearButton)) {
67 String text = "";
68 valueText.setText(text);
69 }
70 }
71 }
The program obtains HelloService through ServiceManager.getService("hello"), and then converts it to the IHelloService interface through the IHelloService.Stub.asInterface function. Among them, the service name "hello" is specified when HelloService is loaded when the system starts, and the IHelloService interface is defined in android.os.IHelloService. For details, please refer to Adding hardware access services to the Application Frameworks layer of the Android system on Ubuntu one article. This program provides a simple function of reading the value of the custom hardware register val, which is implemented through the two interfaces of IHelloService.getVal and IHelloService.setVal.
1 <?xml version="1.0" encoding="utf-8"?> 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 3 android:orientation="vertical" 4 android:layout_width="fill_parent" 5 android:layout_height="fill_parent"> 6 <LinearLayout 7 android:layout_width="fill_parent" 8 android:layout_height="wrap_content" 9 android:orientation="vertical" 10 android:gravity="center"> 11 <TextView 12 android:layout_width="wrap_content" 13 android:layout_height="wrap_content" 14 android:text="@string/value"> 15 </TextView> 16 <EditText 17 android:layout_width="fill_parent" 18 android:layout_height="wrap_content" 19 android:id="@+id/edit_value" 20 android:hint="@string/hint"> 21 </EditText> 22 </LinearLayout> 23 <LinearLayout 24 android:layout_width="fill_parent" 25 android:layout_height="wrap_content" 26 android:orientation="horizontal" 27 android:gravity="center"> 28 <Button 29 android:id="@+id/button_read" 30 android:layout_width="wrap_content" 31 android:layout_height="wrap_content" 32 android:text="@string/read"> 33 </Button> 34 <Button 35 android:id="@+id/button_write" 36 android:layout_width="wrap_content" 37 android:layout_height="wrap_content" 38 android:text="@string/write"> 39 </Button> 40 <Button 41 android:id="@+id/button_clear" 42 android:layout_width="wrap_content" 43 android:layout_height="wrap_content" 44 android:text="@string/clear"> 45 </Button> 46 </LinearLayout> 47 </LinearLayout>
String file res/values/strings.xml:
1 <?xml version="1.0" encoding="utf-8"?> 2 <resources> 3 <string name="app_name">Hello</string> 4 <string name="value">Value</string> 5 <string name="hint">Please input a value...</string> 6 <string name="read">Read</string> 7 <string name="write">Write</string> 8 <string name="clear">Clear</string> 9 </resources>
Program description file AndroidManifest.xml:
1 <?xml version="1.0" encoding="utf-8"?> 2 <manifest xmlns:android="http://schemas.android.com/apk/res/android" 3 package="shy.luo.hello" 4 android:versionCode="1" 5 android:versionName="1.0"> 6 <application android:icon="@drawable/icon" android:label="@string/app_name"> 7 <activity android:name=".Hello" 8 android:label="@string/app_name"> 9 <intent-filter> 10 <action android:name="android.intent.action.MAIN" /> 11 <category android:name="android.intent.category.LAUNCHER" /> 12 </intent-filter> 13 </activity> 14 </application> 15 </manifest>
5. Repackage the system image file system.img:
The repackaged system.img file has the Hello.apk file built in.
