Android之查看网络图片和网页HTML

小鱼儿 2022-07-28 01:46 180阅读 0赞

### 网络编程是Android应用中很重要的一部分，本文主要讲述了利用HttpURLConnection获取网络图片和HTML的方法。 ###

### 获取网络图片 ###

public class MainActivity extends Activity implements OnClickListener {
        
    
        private static final String TAG = "MainActivity";
        protected static final int ERROR = 1;
        private EditText etUrl;
        private ImageView ivIcon;
        private final int SUCCESS = 0;
    
        private Handler handler = new Handler() {
    
            /**
             * 接收消息
             */
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
    
                Log.i(TAG, "what = " + msg.what);
                if(msg.what == SUCCESS) {   // 当前是访问网络, 去显示图片
                    ivIcon.setImageBitmap((Bitmap) msg.obj);        // 设置imageView显示的图片
                } else if(msg.what == ERROR) {
                    Toast.makeText(MainActivity.this, "抓去失败", 0).show();
                }
            }
        };
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            ivIcon = (ImageView) findViewById(R.id.iv_icon);
            etUrl = (EditText) findViewById(R.id.et_url);
    
            findViewById(R.id.btn_submit).setOnClickListener(this);
        }
    
        @Override
        public void onClick(View v) {
            final String url = etUrl.getText().toString();
    
            new Thread(new Runnable() {
    
                @Override
                public void run() {
                    Bitmap bitmap = getImageFromNet(url);
    
    //              ivIcon.setImageBitmap(bitmap);      // 设置imageView显示的图片
                    if(bitmap != null) {
                        Message msg = new Message();
                        msg.what = SUCCESS;
                        msg.obj = bitmap;
                        handler.sendMessage(msg);
                    } else {
                        Message msg = new Message();
                        msg.what = ERROR;
                        handler.sendMessage(msg);
                    }
                }}).start();
    
        }
    
        /**
         * 根据url连接取网络抓去图片返回
         * @param url
         * @return url对应的图片
         */
        private Bitmap getImageFromNet(String url) {
            HttpURLConnection conn = null;
            try {
                URL mURL = new URL(url);    // 创建一个url对象
    
                // 得到http的连接对象
                conn = (HttpURLConnection) mURL.openConnection();
    
                conn.setRequestMethod("GET");       // 设置请求方法为Get
                conn.setConnectTimeout(10000);      // 设置连接服务器的超时时间, 如果超过10秒钟, 没有连接成功, 会抛异常
                conn.setReadTimeout(5000);      // 设置读取数据时超时时间, 如果超过5秒, 抛异常
    
                conn.connect();     // 开始链接
    
                int responseCode = conn.getResponseCode(); // 得到服务器的响应码
                if(responseCode == 200) {
                    // 访问成功
                    InputStream is = conn.getInputStream(); // 获得服务器返回的流数据
    
                    Bitmap bitmap = BitmapFactory.decodeStream(is); // 根据 流数据 创建一个bitmap位图对象
    
                    return bitmap;
                } else {
                    Log.i(TAG, "访问失败: responseCode = " + responseCode);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if(conn != null) {
                    conn.disconnect();      // 断开连接
                }
            }
            return null;
        }
    }

### 不能子线程中改变主线程页面，故需要使用Handler ###

### 上面的方法较为烦琐，使用github上的开源库，android-smart-image-view可以有效的实现相同的功能，同时简化操作，使用方法是将开源库src文件夹下的内容复制一份到工程中,同时在布局文件中，使用全类名使用自定义控件SmartImageView即可. ###

### android-smart-image-view实现 ###

public class MainActivity2 extends Activity implements OnClickListener {
        
    
        private EditText etUrl;
        private SmartImageView mImageView;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main2);
    
            etUrl = (EditText) findViewById(R.id.et_url);
            mImageView = (SmartImageView) findViewById(R.id.iv_icon);
    
            findViewById(R.id.btn_submit).setOnClickListener(this);
        }
    
        @Override
        public void onClick(View v) {
    
            // 1. 取出url, 抓取图片
            String url = etUrl.getText().toString();
    
            mImageView.setImageUrl(url);
        }
    }

### 查看网页HTML实现 ###

public class MainActivity extends Activity {
        
    
        private static final String TAG = "MainActivity";
        private static final int SUCCESS = 0;
        protected static final int ERROR = 1;
        private EditText etUrl;
        private TextView tvHtml;
    
        private Handler handler = new Handler() {
    
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);
                switch (msg.what) {
                case SUCCESS:
                     tvHtml.setText((String) msg.obj);
                    break;
                case ERROR:
                    Toast.makeText(MainActivity.this, "访问失败", 0).show();
                    break;
                default:
                    break;
                }
            }
    
        };
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            etUrl = (EditText) findViewById(R.id.et_url);
            tvHtml = (TextView) findViewById(R.id.tv_html);
    
        }
    
        public void getHtml(View v) {
            final String url = etUrl.getText().toString();
    
            new Thread(new Runnable() {
    
                @Override
                public void run() {
                    // 请求网络
                    String html = getHtmlFromInternet(url);
    
                    if(!TextUtils.isEmpty(html)) {
                        // 更新textview的显示了
                        Message msg = new Message();
                        msg.what = SUCCESS;
                        msg.obj = html;
                        handler.sendMessage(msg);
                    } else {
                        Message msg = new Message();
                        msg.what = ERROR;
                        handler.sendMessage(msg);
                    }
                }
            }).start();
        }
    
        /**
         * 根据给定的url访问网络, 抓去html代码
         * @param url
         * @return
         */
        protected String getHtmlFromInternet(String url) {
    
            try {
                URL mURL = new URL(url);
                HttpURLConnection conn = (HttpURLConnection) mURL.openConnection();
    
                conn.setRequestMethod("GET");
                conn.setConnectTimeout(10000);
                conn.setReadTimeout(5000);
    
    //          conn.connect();
    
                int responseCode = conn.getResponseCode();
    
                if(responseCode == 200) {
                    InputStream is = conn.getInputStream();
                    String html = getStringFromInputStream(is);
                    return html;
                } else {
                    Log.i(TAG, "访问失败: " + responseCode);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }
    
        /**
         * 根据流返回一个字符串信息
         * @param is
         * @return
         * @throws IOException 
         */
        private String getStringFromInputStream(InputStream is) throws IOException {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] buffer = new byte[1024];
            int len = -1;
    
            while((len = is.read(buffer)) != -1) {
                baos.write(buffer, 0, len);
            }
            is.close();
    
            String html = baos.toString();  // 把流中的数据转换成字符串, 采用的编码是: utf-8
    
            String charset = "utf-8";
            if(html.contains("gbk") || html.contains("gb2312")
                    || html.contains("GBK") || html.contains("GB2312")) {       // 如果包含gbk, gb2312编码, 就采用gbk编码进行对字符串编码
                charset = "gbk";
            }
    
            html = new String(baos.toByteArray(), charset); // 对原有的字节数组进行使用处理后的编码名称进行编码
            baos.close();
            return html;
        }
    }

### 使用这种方法HTML有时会产生乱码，解决方法如上 ###

### 完成 ###