1.内容观察者ContentObserver如果ContentProvider的访问者需要知道ContentProvider中的数据发生了变化，可以在ContentProvider 发生数据变化时调用getContentResolver().notifyChange(uri, null)来通知注册在此URI上的访问者，例子如下：private static final Uri URI = Uri.parse("content://person.db");public class PersonContentProvider extends ContentProvider {    public Uri insert(Uri uri, ContentValues values) {        db.insert("person", "personid", values);        getContext().getContentResolver().notifyChange(uri, null);    }}如果ContentProvider的访问者需要得到数据变化通知，必须使用ContentObserver对数据（数据采用uri描述）进行监听，当监听到数据变化通知时，系统就会调用ContentObserver的onChange()方法：getContentResolver().registerContentObserver(Uri.parse("content://person.db"),                true, new PersonObserver(new Handler()));public class PersonObserver extends ContentObserver{    public PersonObserver(Handler handler) {        super(handler);     }    public void onChange(boolean selfChange) {        //此处可以进行相应的业务处理        Toast.makeText(MainActivity.this, "数据库内容发送变化了！", 0).show();    }}2.获取系统的联系人信息public void getContacts(View view) {        ContentResolver resolver = this.getContentResolver();        Uri uri = Uri.parse("content://com.android.contacts/raw_contacts");        Uri dataUri = Uri.parse("content://com.android.contacts/data");        Cursor cursor = resolver.query(uri, null, null, null, null);        if (cursor.moveToLast()) {            String id = cursor.getString(cursor.getColumnIndex("contact_id"));            if (id != null) {                Cursor dataCursor = resolver.query(dataUri, null,"raw_contact_id=?", new String[] { id }, null);                while (dataCursor.moveToNext()) {                    String data1 = dataCursor.getString(dataCursor.getColumnIndex("data1"));                    String mimetype = dataCursor.getString(dataCursor.getColumnIndex("mimetype"));                    Toast.makeText(this, data1 + " = " + mimetype, 0).show();                }                dataCursor.close();            } else {                Toast.makeText(this, "空！", 0).show();            }        }        cursor.close();    }     <uses-permission android:name="android.permission.READ_CONTACTS" />  3.保存联系人到系统通讯录 public void writeContact(View view) {        ContentResolver resolver = this.getContentResolver();        Uri uri = Uri.parse("content://com.android.contacts/raw_contacts");        Uri dataUri = Uri.parse("content://com.android.contacts/data");        Cursor cursor = resolver.query(uri, new String[] { "_id" }, null, null,                null);        if (cursor.moveToLast()) {            int lastId = cursor.getInt(0);            int newId = lastId + 1;            ContentValues values = new ContentValues();            values.put("contact_id", newId);            resolver.insert(uri, values);            ContentValues phoneValues = new ContentValues();            phoneValues.put("data1", "13500001111");            phoneValues.put("mimetype", "vnd.android.cursor.item/phone_v2");            phoneValues.put("raw_contact_id", newId);            resolver.insert(dataUri, phoneValues);            ContentValues emaiValues = new ContentValues();            emaiValues.put("data1", "reality_jie@qq.com");            emaiValues.put("mimetype", "vnd.android.cursor.item/email_v2");            emaiValues.put("raw_contact_id", newId);            resolver.insert(dataUri, emaiValues);            ContentValues nameValues = new ContentValues();            nameValues.put("data1", "weijie");            nameValues.put("mimetype", "vnd.android.cursor.item/name");            nameValues.put("raw_contact_id", newId);            resolver.insert(dataUri, nameValues);        }        cursor.close();        Toast.makeText(this, "保存成功", 0).show();    }    <uses-permission android:name="android.permission.WRITE_CONTACTS" />4.网络图片查看器public class MainActivity extends Activity {        protected static final int UPDATE_UI = 1;        protected static final int ERROR = 2;        private ImageView iv_beauty;        private EditText et_path;        // 主线程创建消息处理器        Handler handler = new Handler() {            @Override            public void handleMessage(Message msg) {                if (msg.what == UPDATE_UI) {                    iv_beauty.setImageBitmap((Bitmap) msg.obj);                } else {                    Toast.makeText(getApplicationContext(), "图片获取失败！", 0)                            .show();                }            }        };        @Override        protected void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            this.iv_beauty = (ImageView) this.findViewById(R.id.iv_beauty);            this.et_path = (EditText) this.findViewById(R.id.et_path);        }        public void watch(View view) {            final String path = this.et_path.getText().toString().trim();            if (TextUtils.isEmpty(path)) {                Toast.makeText(this, "路径不能为空", 0).show();            } else {                new Thread() {                    @Override                    public void run() {                        try {                            URL url = new URL(path);                            HttpURLConnection connection = (HttpURLConnection) url                                    .openConnection();                            // 设置请求方式                            connection.setRequestMethod("GET");                            // 设置超时时间                            connection.setConnectTimeout(10000);                            // connection.setRequestProperty(field, newValue)                            int code = connection.getResponseCode();                            if (code == 200) {                                InputStream is = connection.getInputStream();                                Bitmap bitmap = BitmapFactory.decodeStream(is);                                // 告诉主线程一个消息，帮我更新ui，内容：bitmap                                Message msg = new Message();                                msg.what = UPDATE_UI;                                msg.obj = bitmap;                                handler.sendMessage(msg);                            } else {                                Message msg = new Message();                                msg.what = ERROR;                                handler.sendMessage(msg);                            }                        } catch (Exception e) {                            e.printStackTrace();                            Message msg = new Message();                            msg.what = ERROR;                            handler.sendMessage(msg);                        }                    }                }.start();            }        }    }5.网络html查看器<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".MainActivity" >    <EditText        android:id="@+id/et_path"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="请输入网址" />    <Button        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="确定"        android:onClick="click" />    <ScrollView        android:layout_width="match_parent"        android:layout_height="match_parent" >        <TextView            android:id="@+id/tv_content"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />    </ScrollView></LinearLayout>public class MainActivity extends Activity {        protected static final int ERROR = 0;        protected static final int SHOW_CONTENT = 1;        private EditText et_path;        private TextView tv_content;        private Handler handler = new Handler() {            public void handleMessage(android.os.Message msg) {                switch (msg.what) {                case ERROR:                    Toast.makeText(MainActivity.this, "获取网页信息失败",                            Toast.LENGTH_SHORT).show();                    break;                case SHOW_CONTENT:                    tv_content.setText((String) msg.obj);                    break;                }            };        };        @Override        protected void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            this.et_path = (EditText) this.findViewById(R.id.et_path);            this.tv_content = (TextView) this.findViewById(R.id.tv_content);        }        public void click(View view) {            final String path = this.et_path.getText().toString().trim();            if (TextUtils.isEmpty(path)) {                Toast.makeText(this, "路径不能为空！", Toast.LENGTH_SHORT).show();            } else {                new Thread() {                    public void run() {                        try {                            URL url = new URL(path);                            HttpURLConnection conn = (HttpURLConnection) url                                    .openConnection();                            conn.setRequestMethod("GET");                            conn.setReadTimeout(5000);                            int code = conn.getResponseCode();                            if (code == 200) {                                InputStream is = conn.getInputStream();                                String result = StreamTool.readInputStream(is);                                Message msg = new Message();                                msg.what = SHOW_CONTENT;                                msg.obj = result;                                handler.sendMessage(msg);                            } else {                                Message msg = new Message();                                msg.what = ERROR;                                handler.sendMessage(msg);                            }                        } catch (Exception e) {                            e.printStackTrace();                            Message msg = new Message();                            msg.what = ERROR;                            handler.sendMessage(msg);                        }                    };                }.start();            }        }    }    public class StreamTool {    public static String readInputStream(InputStream is) {        try {            ByteArrayOutputStream out = new ByteArrayOutputStream();            int length = 0;            byte[] buffer = new byte[1024];            if ((length = is.read(buffer)) != -1) {                out.write(buffer, 0, length);            }            byte[] result = out.toByteArray();            String temp = new String(result);//默认utf-8            if(temp.contains("gb2312")){                return new String(result,"gb2312");            }            return temp;        } catch (Exception e) {            // TODO: handle exception        }        return "转换失败";    }}<uses-permission android:name="android.permission.INTERNET"/>6.使用异步框架Android-Async-Http1、下载：https://github.com/loopj/android-async-http2、在工程中加入jar包，或直接把源文件加到工程中3、android-async-http文档：http://loopj.com/android-async-http/AsyncHttp使用回调的方法处得请求的结果。AsyncHttpClient client = new AsyncHttpClient();client.get("http://www.google.com", new AsyncHttpResponseHandler() {    @Override    public void onSuccess(String response) {        System.out.println(response);    }});最好建一个静态的AsyncHttpClientpublic class HttpUtil {    private static AsyncHttpClient client = new AsyncHttpClient(); // 实例话对象    static {        client.setTimeout(10000); // 设置链接超时，如果不设置，默认为10s    }    // 用一个完整url获取一个string对象    public static void get(String urlString, AsyncHttpResponseHandler res)     {        client.get(urlString, res);    }    // url里面带参数    public static void get(String urlString, RequestParams params,            AsyncHttpResponseHandler res){        client.get(urlString, params, res);    }    // 不带参数，获取json对象或者数组    public static void get(String urlString, JsonHttpResponseHandler res) {        client.get(urlString, res);    }    // 带参数，获取json对象或者数组    public static void get(String urlString, RequestParams params,            JsonHttpResponseHandler res) {        client.get(urlString, params, res);    }    // 下载数据使用，会返回byte数据    public static void get(String uString, BinaryHttpResponseHandler bHandler) {        client.get(uString, bHandler);    }    public static AsyncHttpClient getClient(){        return client;    }}下载：     public void downloadClick(View view) {        String url = "http://f.hiphotos.baidu.com/album/w%3D2048/sign=38c43ff7902397ddd6799f046dbab3b7/9c16fdfaaf51f3dee973bf7495eef01f3b2979d8.jpg";        HttpUtil.get(url, new BinaryHttpResponseHandler() {            @Override            public void onSuccess(byte[] arg0) {                super.onSuccess(arg0);                File file = Environment.getExternalStorageDirectory();                File file2 = new File(file, "cat");                file2.mkdir();                file2 = new File(file2, "cat.jpg");                try {                    FileOutputStream oStream = new FileOutputStream(file2);                    oStream.write(arg0);                    oStream.flush();                    oStream.close();                    textView.setText("可爱的猫咪已经保存在sdcard里面");                } catch (Exception e) {                    e.printStackTrace();                    Log.i("hck", e.toString());                }            }        });    }    上传：    public void uploadClick(View view){        String path="http://10.0.2.2:8080/jsontest/servlet/UploadServlet";        File myFile = new File("/sdcard/cat/cat.jpg");        RequestParams params = new RequestParams();        try {            params.put("filename", myFile);                        AsyncHttpClient client = new AsyncHttpClient();            client.post(path, params, new AsyncHttpResponseHandler(){                @Override                public void onSuccess(int statusCode, String content) {                    // TODO Auto-generated method stub                    super.onSuccess(statusCode, content);                    Toast.makeText(MainActivity.this, "上传成功！", Toast.LENGTH_LONG).show();                }                                            });                    } catch(FileNotFoundException e) {                    }    }