1、开发Android应用程序来使用硬件访问服务

      ~/android-2.3_r1/packages/experimental/Freg

      ----AndroidManifest.java

      ----Android.mk

      ----src

              ----shy/luo/freg

                        ----Freg.java

      ----res

             ----layout

                        ----main.xml

      ----values

            ----string.xml

      ----drawable

            ----icon.png

      Freg.java

package shy.luo.freg;

import android.app.Activity;
import android.os.ServiceManager;
import android.os.Bundle;
import android.os.IFregService;
import android.os.RemoteException;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class Freg extends Activity implements OnClickListener {
	private final static String LOG_TAG = "shy.luo.freg.FregActivity";
	
	private IFregService fregService = null;

	private EditText valueText = null;
	private Button readButton = null;
	private Button writeButton = null;
	private Button clearButton = null;
	
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

	fregService = IFregService.Stub.asInterface(
		ServiceManager.getService("freg"));
        
        valueText = (EditText)findViewById(R.id.edit_value);
        readButton = (Button)findViewById(R.id.button_read);
        writeButton = (Button)findViewById(R.id.button_write);
        clearButton = (Button)findViewById(R.id.button_clear);

	readButton.setOnClickListener(this);
	writeButton.setOnClickListener(this);
	clearButton.setOnClickListener(this);
        
        Log.i(LOG_TAG, "Freg Activity Created");
    }
    
    @Override
    public void onClick(View v) {
    	if(v.equals(readButton)) {
		try {
    			int val = fregService.getVal();
    			String text = String.valueOf(val);
    			valueText.setText(text);
		} catch (RemoteException e) {
			Log.e(LOG_TAG, "Remote Exception while reading value from freg service.");
		}		
    	}
    	else if(v.equals(writeButton)) {
		try {
    			String text = valueText.getText().toString();
    			int val = Integer.parseInt(text);
			fregService.setVal(val);
		} catch (RemoteException e) {
			Log.e(LOG_TAG, "Remote Exception while writing value to freg service.");
		}
    	}
    	else if(v.equals(clearButton)) {
    		String text = "";
    		valueText.setText(text);
    	}
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <LinearLayout
    	android:layout_width="fill_parent"
    	android:layout_height="wrap_content"
    	android:orientation="vertical" 
    	android:gravity="center">
    	<TextView 
			android:layout_width="wrap_content"
       		android:layout_height="wrap_content" 
        	android:text="@string/value">
    	</TextView>
    	<EditText 
     		android:layout_width="fill_parent"
        	android:layout_height="wrap_content" 
        	android:id="@+id/edit_value"
        	android:hint="@string/hint">
    	</EditText>
    </LinearLayout>
     <LinearLayout
    	android:layout_width="fill_parent"
    	android:layout_height="wrap_content"
    	android:orientation="horizontal" 
    	android:gravity="center">
    	<Button 
    		android:id="@+id/button_read"
    		android:layout_width="wrap_content"
    		android:layout_height="wrap_content"
    		android:text="@string/read">
    	</Button>
    	<Button 
    		android:id="@+id/button_write"
    		android:layout_width="wrap_content"
    		android:layout_height="wrap_content"
    		android:text="@string/write">
    	</Button>
    	<Button 
    		android:id="@+id/button_clear"
    		android:layout_width="wrap_content"
    		android:layout_height="wrap_content"
    		android:text="@string/clear">
    	</Button>
    </LinearLayout>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">Freg</string>
    <string name="value">Value</string>
    <string name="hint">Please input a value...</string>
    <string name="read">Read</string>
    <string name="write">Write</string>
    <string name="clear">Clear</string>
</resources>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="shy.luo.freg"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Freg"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest> 

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := optional

LOCAL_SRC_FILES := $(call all-subdir-java-files)

LOCAL_PACKAGE_NAME := Freg

include $(BUILD_PACKAGE)

      编译成apk：

      生成的Freg.apk位于out/target/product/generic/system/app中。

      打包：

      最后把Freg.apk重新打包进入system.img，位于out/target/product/gerneric中。

      运行：

      结果如下：