网络编程之get，post请求，文件上传及下载

* 1.发送GET请求
AsyncHttpClient.get(), 使用RequestParams传递数据
  * 2.发送POST请求
AsyncHttpClient.post(), 使用RequestParams传递数据
3.访问Webservice
Webservice就是别人写好的, 已经发布在网络上的公开的API, 应用程序中可以直接调用
4.上传
在RequestParams中添加一个File类型的字段, AsyncHttpClient就会执行上传操作
5.下载
请求下载路径, 使用FileAsyncHttpResponseHandler来处理下载文件
post请求代码：

package com.itheima.request;
import java.io.File;
import org.apache.http.Header;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.AsyncHttpResponseHandler;
import com.loopj.android.http.RequestParams;
public class MainActivity extends Activity {
private EditText usernameET;
private EditText passwordET;
private EditText pathET;
private AsyncHttpClient client;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
usernameET = (EditText) findViewById(R.id.usernameET);
passwordET = (EditText) findViewById(R.id.passwordET);
pathET = (EditText) findViewById(R.id.pathET);
client = new AsyncHttpClient();
}
public void login(View v) throws Exception {
String username = usernameET.getText().toString().trim();
String password = passwordET.getText().toString().trim();
String path = pathET.getText().toString().trim();
//带参数的请求；
RequestParams params = new RequestParams();
params.put("username", username);
// URLEncoder.encode()
params.put("password", password);
params.put("upload", new File(path));	// File类型会作为上传文件字段
//post请求，如果为get请求，则调用get方法；
client.post("http://192.168.1.251:8080/WebServer/LoginServlet", params , new AsyncHttpResponseHandler() {
public void onSuccess(int statusCode, Header[] headers, byte[] responseBody) {
Toast.makeText(getApplicationContext(), "登录成功", Toast.LENGTH_SHORT).show();
}
public void onFailure(int statusCode, Header[] headers, byte[] responseBody, Throwable error) {
Toast.makeText(getApplicationContext(), "登录失败 " + statusCode, Toast.LENGTH_SHORT).show();
error.printStackTrace();
}
});
}
}

文件下载代码：

<pre name="code" class="java">package com.itheima.download;
import java.io.File;
import org.apache.http.Header;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.FileAsyncHttpResponseHandler;
public class MainActivity extends Activity {
private EditText pathET;
private AsyncHttpClient client;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pathET = (EditText) findViewById(R.id.pathET);
client = new AsyncHttpClient();
}
public void download(View v) {
String path = pathET.getText().toString().trim();
//文件下载的保存地址；
File file = new File("/mnt/sdcard/", path.substring(path.lastIndexOf("/") + 1));
client.get(path, new FileAsyncHttpResponseHandler(file) {
// 处理文件传输的处理器
public void onSuccess(int statusCode, Header[] headers, File file) {
Toast.makeText(getApplicationContext(), "下载成功", Toast.LENGTH_SHORT).show();
}
public void onFailure(int statusCode, Header[] headers, Throwable throwable, File file) {
Toast.makeText(getApplicationContext(), "下载失败 " + statusCode, Toast.LENGTH_SHORT).show();
throwable.printStackTrace();
}
public void onProgress(int bytesWritten, int totalSize) {	// 下载或上传的进度
System.out.println(bytesWritten + " / " + totalSize + " (" + bytesWritten * 100 / totalSize + "%)");
}
});
}
}

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