Android网络实例:HTTP之利用HttpURLConnection访问百度、获取网络图片

MianActivity.java

public class MainActivity extends AppCompatActivity {
Button visitWebBtn = null;
Button downImgBtn = null;
TextView showTextView = null;
ImageView showImageView = null;
String resultStr = “”;
ProgressBar progressBar = null;
ViewGroup viewGroup = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initUI();
visitWebBtn.setOnClickListener(new View.OnClickListener(){

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            showImageView.setVisibility(View.GONE);
            showTextView.setVisibility(View.VISIBLE);
            Thread visitBaiduThread = new Thread(new VisitWebRunnable());
            visitBaiduThread.start();
            try {
                visitBaiduThread.join();
                if(!resultStr.equals("")){
                    showTextView.setText(resultStr);
                }
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    });
    downImgBtn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            showImageView.setVisibility(View.VISIBLE);
            showTextView.setVisibility(View.GONE);
            String imgUrl = "https://ss3.bdstatic.com/70cFv8Sh_Q1YnxGkpoWK1HF6hhy/it/u=112912491,3646496790&fm=26&gp=0.jpg";
            new DownImgAsyncTask().execute(imgUrl);
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
   // getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
public void initUI(){
    showTextView = (TextView)findViewById(R.id.textview_show);
    showImageView = (ImageView)findViewById(R.id.imagview_show);
    downImgBtn = (Button)findViewById(R.id.btn_download_img);
    visitWebBtn = (Button)findViewById(R.id.btn_visit_web);
}
/**
 * 获取指定URL的响应字符串
 * @param urlString
 * @return
 */
private String getURLResponse(String urlString){
    HttpURLConnection conn = null; //连接对象
    InputStream is = null;
    String resultData = "";
    try {
        URL url = new URL(urlString); //URL对象
        conn = (HttpURLConnection)url.openConnection(); //使用URL打开一个链接
        conn.setDoInput(true); //允许输入流，即允许下载
        conn.setDoOutput(true); //允许输出流，即允许上传
        conn.setUseCaches(false); //不使用缓冲
        conn.setRequestMethod("GET"); //使用get请求
        is = conn.getInputStream();   //获取输入流，此时才真正建立链接
        InputStreamReader isr = new InputStreamReader(is);
        BufferedReader bufferReader = new BufferedReader(isr);
        String inputLine  = "";
        while((inputLine = bufferReader.readLine()) != null){
            resultData += inputLine + "\n";
        }

    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }finally{
        if(is != null){
            try {
                is.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(conn != null){
            conn.disconnect();
        }
    }

    return resultData;
}

/**
 * 从指定URL获取图片
 * @param url
 * @return
 */
private Bitmap getImageBitmap(String url){
    URL imgUrl = null;
    Bitmap bitmap = null;
    try {
        imgUrl = new URL(url);
        HttpURLConnection conn = (HttpURLConnection)imgUrl.openConnection();
        conn.setDoInput(true);
        conn.connect();
        InputStream is = conn.getInputStream();
        bitmap = BitmapFactory.decodeStream(is);
        is.close();
    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }catch(IOException e){
        e.printStackTrace();
    }
    return bitmap;
}
class VisitWebRunnable implements Runnable{

    @Override
    public void run() {
        // TODO Auto-generated method stub
        String data = getURLResponse("http://www.baidu.com/");
        resultStr = data;
    }

}
class DownImgAsyncTask extends AsyncTask {


    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        showImageView.setImageBitmap(null);
        showProgressBar();//显示进度条提示框

    }

    @Override
    protected Bitmap doInBackground(String... params) {
        // TODO Auto-generated method stub
        Bitmap b = getImageBitmap(params[0]);
        return b;
    }

    @Override
    protected void onPostExecute(Bitmap result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        if(result!=null){
            dismissProgressBar();
            showImageView.setImageBitmap(result);
        }
    }



}
/**
 * 在母布局中间显示进度条
 */
private void showProgressBar(){
    progressBar = new ProgressBar(this, null, android.R.attr.progressBarStyleLarge);
    RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,
            ViewGroup.LayoutParams.WRAP_CONTENT);
    params.addRule(RelativeLayout.CENTER_IN_PARENT,  RelativeLayout.TRUE);
    progressBar.setVisibility(View.VISIBLE);
    Context context = getApplicationContext();
    viewGroup = (ViewGroup)findViewById(R.id.parent_view);
    //		MainActivity.this.addContentView(progressBar, params);
    viewGroup.addView(progressBar, params);
}
/**
 * 隐藏进度条
 */
private void dismissProgressBar(){
    if(progressBar != null){
        progressBar.setVisibility(View.GONE);
        viewGroup.removeView(progressBar);
        progressBar = null;
    }
}

}

activity_main.xml