引用：http://note.sdo.com/u/1500295617/n/prb71~jlUsM0LX01o000br

引用：http://ysongren.blog.163.com/blog/static/615422072010112263112511/

安装： 
String str = "/CanavaCancel.apk"; 
String fileName = Environment.getExternalStorageDirectory() + str; 
Intent intent = new Intent(Intent.ACTION_VIEW); 
intent.setDataAndType(Uri.fromFile(new File(fileName)), "application/vnd.android.package-archive"); 
startActivity(intent);
卸载：
Uri packageURI = Uri.parse("package:com.demo.CanavaCancel");   
Intent uninstallIntent = new Intent(Intent.ACTION_DELETE, packageURI);   
startActivity(uninstallIntent);


Environment拥有一些可以获取环境变量的方法 
package:com.demo.CanavaCancel 这个形式是 package:程序完整的路径 (包名+程序名).
//下载apk程序代码
protected File downLoadFile(String httpUrl) {
                // TODO Auto-generated method stub
                final String fileName = "updata.apk";
                File tmpFile = new File("/sdcard/update");
                if (!tmpFile.exists()) {
                        tmpFile.mkdir();
                }
                final File file = new File("/sdcard/update/" + fileName);

                try {
                        URL url = new URL(httpUrl);
                        try {
                                HttpURLConnection conn = (HttpURLConnection) url
                                                .openConnection();
                                InputStream is = conn.getInputStream();
                                FileOutputStream fos = new FileOutputStream(file);
                                byte[] buf = new byte[256];
                                conn.connect();
                                double count = 0;
                                if (conn.getResponseCode() >= 400) {
                                        Toast.makeText(Main.this, "连接超时", Toast.LENGTH_SHORT)
                                                        .show();
                                } else {
                                        while (count <= 100) {
                                                if (is != null) {
                                                        int numRead = is.read(buf);
                                                        if (numRead <= 0) {
                                                                break;
                                                        } else {
                                                                fos.write(buf, 0, numRead);
                                                        }

                                                } else {
                                                        break;
                                                }

                                        }
                                }

                                conn.disconnect();
                                fos.close();
                                is.close();
                        } catch (IOException e) {
                                // TODO Auto-generated catch block

                                e.printStackTrace();
                        }
                } catch (MalformedURLException e) {
                        // TODO Auto-generated catch block

                        e.printStackTrace();
                }

                return file;
        }
//打开APK程序代码

private void openFile(File file) {
                // TODO Auto-generated method stub
                Log.e("OpenFile", file.getName());
                Intent intent = new Intent();
                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                intent.setAction(android.content.Intent.ACTION_VIEW);
                intent.setDataAndType(Uri.fromFile(file),
                                "application/vnd.android.package-archive");
                startActivity(intent);
        }