Android网络连线之HttpURLConnection【从网页获取图片 demo】

概述从网页获取图片效果是这样，下面是代码：layout<?xmlversion="1.0"encoding="utf-8"?><LinearLayoutxmlns:android="http://schemas.android.com/apkes/android"android:orientation="vertical"android:layout_width=&quo 从网页获取图片

效果是这样，下面是代码：

layout

<?xml version="1.0" enCoding="utf-8"?><linearLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"    androID:orIEntation="vertical"    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent" >    <EditText        androID:layout_wIDth="match_parent"        androID:layout_height="wrap_content"        androID:ID="@+ID/et_target"        androID:text="https://bkimg.cdn.bcebos.com/pic/574e9258d109b3de43046931c3bf6c81800a4c34?x-bce-process=image/resize,m_lfit,w_500,h_500,limit_1"        />    <button        androID:layout_wIDth="match_parent"        androID:layout_height="wrap_content"        androID:text="visualizer"        androID:onClick="visualizer"/>    <ImageVIEw        androID:layout_wIDth="wrap_content"        androID:layout_height="wrap_content"        androID:ID="@+ID/iv_result"        /></linearLayout>

StreamUtility（把流写在文件上）

public class StreamUtility {    public static voID writeStream2file (inputStream in, file file) throws Exception {        fileOutputStream outputStream = new fileOutputStream(file);        int len= -1;        byte[] buffer = new byte[1024];        while ((len= in.read(buffer)) !=-1){            outputStream.write(buffer,0,len);        }        outputStream.close();        in.close();    }}

Mainactivity.java

因为子线程不能更新ui，这里有两种方法

1.线程之间通讯构建第三方，利用handler传给主线程再更新ui
2.用runonUIThread方法，直接在子线程更新ui

public class MainActivity extends AppCompatActivity {    private EditText et_target;    private ImageVIEw iv_result;    private Handler handler =new Handler(){        @OverrIDe        public voID handleMessage( Message msg) {            switch (msg.what){                case RESPONSE_SUCCESS:                    Bitmap result = (Bitmap) msg.obj;                    iv_result.setimageBitmap(result);                    break;                case RESPONSE_Failed:                    Toast.makeText(MainActivity.this, "失败"+msg.arg1, Toast.LENGTH_SHORT).show();                    break;                case RESPONSE_EXCEPTION:                    Toast.makeText(MainActivity.this, "异常", Toast.LENGTH_SHORT).show();                    break;            }        }    };    private  final int RESPONSE_SUCCESS=1;    private  final int RESPONSE_Failed=2;    private  final int RESPONSE_EXCEPTION=3;    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_main);        et_target = (EditText) findVIEwByID(R.ID.et_target);        iv_result = (ImageVIEw) findVIEwByID(R.ID.iv_result);    }    public voID visualizer(VIEw vIEw) {        final String path = et_target.getText().toString().trim();            final file file = new file(getCacheDir(), Base64.encodetoString(path.getBytes(),Base64.DEFAulT));/*缓存cache*//*现在没产生文件，写名，开流时候才产生*/        /*base64应用原因 1.转换成的字符串没有特殊字符2.加密好的也是唯一的，不能重复3.加密后的固定长度*/        if (file.exists() && file.length()>0){            Bitmap bitmap = BitmapFactory.decodefile(file.getabsolutePath());            iv_result.setimageBitmap(bitmap);            System.out.println("-----------------cache");            return;        }        new Thread(){            @OverrIDe            public voID run() {                httpURLConnection connection = null;                try {                    URL url = new URL(path);                     connection = (httpURLConnection) url.openConnection();                    connection.setRequestMethod("GET");                    connection.setConnectTimeout(5000);                    int code = connection.getResponseCode();                    if (code == 200){                        inputStream inputStream = connection.getinputStream();                        StreamUtility.writeStream2file(inputStream,file);/*把流写入file文件上*/                        /*Message message = new Message();*//*new是最慢的*/                        final Bitmap bitmap = BitmapFactory.decodefile(file.getabsolutePath());/*从本地拿，绝对路径*/                        System.out.println("-----------------newload");                                                runOnUiThread(new Runnable() {                            @OverrIDe                            public voID run() {                                iv_result.setimageBitmap(bitmap);                            }                        });                  /*如果只更新ui用runOnUiThread，如果给主线程发数据只能用handler*/                        /*iv_result.setimageBitmap(BitmapFactory.decodeStream(inputStream));*//*位图，容易崩溃*/                    }else {                        Message msg = Message.obtain();                        msg.arg1=code;                        msg.what=RESPONSE_Failed;                        handler.sendMessage(msg);                    }                } catch (Exception e) {                    handler.sendEmptyMessage(RESPONSE_EXCEPTION);                    e.printstacktrace();                } finally {                    if (connection != null)                    connection.disconnect();                }            }        }.start();    }}

最后在androIDmanifest加上网络权限

 <uses-permission androID:name="androID.permission.INTERNET"/>

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