Android系统本身提供了安装卸载功能，但是api接口是@hide的，不是公开的接口，所以在应用级别
是无法实现静默安装和卸载的，要实现静默安装和卸载需要是系统应用，要有系统签名和相应的权限

简单思路如下：

通过反射获得安装接口installPackage和卸载接口 deletePackage
在自己的包中引入两个接口IPackageInstallObserver和IPackageDeleteObserver的空实现
调用安装卸载的方法，回调上面的两个接口
添加权限
进行系统签名
将应用push到系统中，作为系统应用

在`PackageManager`中的提供的接口如下

安装接口

// @SystemApi
public abstract void installPackage(
   Uri packageURI, IPackageInstallObserver observer, int flags,
   String installerPackageName);

卸载接口

// @SystemApi
public abstract void deletePackage(
   String packageName, IPackageDeleteObserver observer, int flags);

引入两个回掉的空实现

在自己应用的工程中新建一个包android.content.pm,并添加两个文件

IPackageDeleteObserver.java

package android.content.pm;
public interface IPackageDeleteObserver extends android.os.IInterface {
public abstract static class Stub extends android.os.Binder implements android.content.pm.IPackageDeleteObserver {
    public Stub() {
        throw new RuntimeException("Stub!");
    }

    public static android.content.pm.IPackageDeleteObserver asInterface(android.os.IBinder obj) {
        throw new RuntimeException("Stub!");
    }

    public android.os.IBinder asBinder() {
        throw new RuntimeException("Stub!");
    }

    public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply, int flags)
            throws android.os.RemoteException {
        throw new RuntimeException("Stub!");
    }
}

public abstract void packageDeleted(java.lang.String packageName, int returnCode)
        throws android.os.RemoteException;
}

IPackageInstallObserver.java

package android.content.pm;
public interface IPackageInstallObserver extends android.os.IInterface {

public abstract static class Stub extends android.os.Binder implements android.content.pm.IPackageInstallObserver {
    public Stub() {
        throw new RuntimeException("Stub!");
    }

    public static android.content.pm.IPackageInstallObserver asInterface(android.os.IBinder obj) {
        throw new RuntimeException("Stub!");
    }

    public android.os.IBinder asBinder() {
        throw new RuntimeException("Stub!");
    }

    public boolean onTransact(int code, android.os.Parcel data, android.os.Parcel reply, int flags)
            throws android.os.RemoteException {
        throw new RuntimeException("Stub!");
    }
}

public abstract void packageInstalled(java.lang.String packageName, int returnCode)
        throws android.os.RemoteException;
}

自己定义个接口回调

OnPackagedObserver.java

package com.example;
public interface OnPackagedObserver {

public void packageInstalled(String packageName, int returnCode);
public void packageDeleted(String packageName,int returnCode);
}

实现方法

反射接口

PackageManager pm = context.getPackageManager();

Class[] types = new Class[] {Uri.class, IPackageInstallObserver.class, int.class, String.class};
Class[] uninstalltypes = new Class[] {String.class, IPackageDeleteObserver.class, int.class};

Method method = pm.getClass().getMethod("installPackage", types);
Method uninstallmethod = pm.getClass().getMethod("deletePackage", uninstalltypes);

实现回调接口

private OnPackagedObserver onInstalledPackaged;
class PackageInstallObserver extends IPackageInstallObserver.Stub {

public void packageInstalled(String packageName, int returnCode) throws RemoteException {
if (onInstalledPackaged != null) {
  onInstalledPackaged.packageInstalled(packageName, returnCode);
}
}
}

class PackageDeleteObserver extends IPackageDeleteObserver.Stub {

public void packageDeleted(String packageName, int returnCode) throws RemoteException {
if (onInstalledPackaged != null) {
  onInstalledPackaged.packageDeleted(packageName, returnCode);
}
}
}

实现
卸载接口只需要提供要卸载的应用的包名packagename ,安装提供了三个接口

public void uninstallPackage(String packagename) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
  uninstallmethod.invoke(pm, new Object[] {packagename, observerdelete, 0});
}
public void installPackage(String apkFile) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
installPackage(new File(apkFile));
}

public void installPackage(File apkFile) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
if (!apkFile.exists()) throw new IllegalArgumentException();
Uri packageURI = Uri.fromFile(apkFile);
installPackage(packageURI);
}

public void installPackage(Uri apkFile) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
method.invoke(pm, new Object[] {apkFile, observer, INSTALL_REPLACE_EXISTING, null});
}

签名

生成一个apk文件，需要对这个apk文件进行系统签名，由于
是系统应用需要的权限，在开发应用时，如果加载AndroidManifest.xml
中会编译不过，需要先用工具 apktool 工具先把apk文件解压出来，用编辑器在AndroidManifest.xml中加入上面的两个权限，然后在用工具apktool重新打包

具体的使用方法参考 [Android实践 -- Apktool 的使用](http://www.jianshu.com/p/1896307da564)

解压
```
apktool d test.apk
```
修改之后，重新打包
```
apktool b test
```
签名之后的文件，需要在进行系统签名
具体的使用方法请参考 Android实践 -- 对apk进行系统签名
```
java -jar signapk.jar platform.x509.pem platform.pk8 test.apk test_signed.apk
```
将签名之后的文件 push到手机中，需要root权限

具体的代码实现

源码

附录，安装卸载错误码速查

回调中的returnCode在PackageManager中的相关的定义如下：

安装错误码

public static final int INSTALL_SUCCEEDED = 1;
public static final int INSTALL_FAILED_ALREADY_EXISTS = -1;
public static final int INSTALL_FAILED_INVALID_APK = -2;
public static final int INSTALL_FAILED_INVALID_URI = -3;
public static final int INSTALL_FAILED_INSUFFICIENT_STORAGE = -4;
public static final int INSTALL_FAILED_DUPLICATE_PACKAGE = -5;
public static final int INSTALL_FAILED_NO_SHARED_USER = -6;
public static final int INSTALL_FAILED_UPDATE_INCOMPATIBLE = -7;
public static final int INSTALL_FAILED_SHARED_USER_INCOMPATIBLE = -8;
public static final int INSTALL_FAILED_MISSING_SHARED_LIBRARY = -9;
public static final int INSTALL_FAILED_REPLACE_COULDNT_DELETE = -10;
public static final int INSTALL_FAILED_DEXOPT = -11;
public static final int INSTALL_FAILED_OLDER_SDK = -12;
public static final int INSTALL_FAILED_CONFLICTING_PROVIDER = -13;
public static final int INSTALL_FAILED_NEWER_SDK = -14;
public static final int INSTALL_FAILED_TEST_ONLY = -15;
public static final int INSTALL_FAILED_CPU_ABI_INCOMPATIBLE = -16;
public static final int INSTALL_FAILED_MISSING_FEATURE = -17;
public static final int INSTALL_FAILED_CONTAINER_ERROR = -18;
public static final int INSTALL_FAILED_INVALID_INSTALL_LOCATION = -19;
public static final int INSTALL_FAILED_MEDIA_UNAVAILABLE = -20;
public static final int INSTALL_FAILED_VERIFICATION_TIMEOUT = -21;
public static final int INSTALL_FAILED_VERIFICATION_FAILURE = -22;
public static final int INSTALL_FAILED_PACKAGE_CHANGED = -23;
public static final int INSTALL_FAILED_UID_CHANGED = -24;
public static final int INSTALL_FAILED_VERSION_DOWNGRADE = -25;
public static final int INSTALL_FAILED_PERMISSION_MODEL_DOWNGRADE = -26;
public static final int INSTALL_PARSE_FAILED_NOT_APK = -100;
public static final int INSTALL_PARSE_FAILED_BAD_MANIFEST = -101;
public static final int INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION = -102;
public static final int INSTALL_PARSE_FAILED_NO_CERTIFICATES = -103;
public static final int INSTALL_PARSE_FAILED_INCONSISTENT_CERTIFICATES = -104;
public static final int INSTALL_PARSE_FAILED_CERTIFICATE_ENCODING = -105;
public static final int INSTALL_PARSE_FAILED_BAD_PACKAGE_NAME = -106;
public static final int INSTALL_PARSE_FAILED_BAD_SHARED_USER_ID = -107;
public static final int INSTALL_PARSE_FAILED_MANIFEST_MALFORMED = -108;
public static final int INSTALL_PARSE_FAILED_MANIFEST_EMPTY = -109;
public static final int INSTALL_FAILED_INTERNAL_ERROR = -110;
public static final int INSTALL_FAILED_USER_RESTRICTED = -111;
public static final int INSTALL_FAILED_DUPLICATE_PERMISSION = -112;
public static final int INSTALL_FAILED_NO_MATCHING_ABIS = -113;
public static final int NO_NATIVE_LIBRARIES = -114;
public static final int INSTALL_FAILED_ABORTED = -115;

卸载错误码

public static final int DELETE_SUCCEEDED = 1;
public static final int DELETE_FAILED_INTERNAL_ERROR = -1;
public static final int DELETE_FAILED_DEVICE_POLICY_MANAGER = -2;
public static final int DELETE_FAILED_USER_RESTRICTED = -3;
public static final int DELETE_FAILED_OWNER_BLOCKED = -4;
public static final int DELETE_FAILED_ABORTED = -5;