实验 图片查看器

一 实验现象

二 实验部分代码

package com.example.getpic;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import javax.net.ssl.HttpsURLConnection;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.view.Menu;import android.view.View;import android.widget.Button;import android.widget.EditText;import android.widget.ImageView;public class MainActivity extends Activity{   private EditText et_path;   private ImageView iv;   private Button bt;     private Handler handler = new Handler(){public void handleMessage(android.os.Message msg){Bitmap bitmap = (Bitmap) msg.obj;iv.setImageBitmap(bitmap);}    };@Overrideprotected void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);et_path=(EditText) findViewById(R.id.et_path);iv = (ImageView) findViewById(R.id.iv);bt=(Button) findViewById(R.id.button1);}public void click(View v){new Thread(){public void run(){try{String path = et_path.getText().toString().trim(); URL url = new URL(path);HttpURLConnection httpURLConnection = (HttpsURLConnection) url.openConnection();httpURLConnection.setRequestMethod("GET");httpURLConnection.setConnectTimeout(5000);int responsecode=httpURLConnection.getResponseCode();if(responsecode==200){InputStream is =httpURLConnection.getInputStream();Bitmap bitmap =BitmapFactory.decodeStream(is);Message msg = new Message();msg.obj=bitmap;handler.sendMessage(msg);}}catch(Exception e){e.printStackTrace();}}}.start();}@Overridepublic 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;}}

界面设计

  <ImageView        android:id="@+id/iv"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentTop="true"        android:layout_centerHorizontal="true"        android:layout_marginTop="78dp"        android:src="@drawable/ic_launcher" />    <Button        android:id="@+id/button1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentBottom="true"        android:layout_centerHorizontal="true"        android:layout_marginBottom="25dp"        android:onClick="click"        android:text="查看" />    <EditText        android:id="@+id/et_path"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_above="@+id/button1"        android:layout_centerHorizontal="true"        android:ems="10"        android:text="https://ss0.bdstatic.com/5aV1bjqh_Q23odCf/static/superman/img/logo/bd_logo1_31bdc765.png" />

三  实验后体会

首先不能忘记添加权限：android.permission.INTERNET   

由于android下的网络连接不能在主线程操作，另外UI的改变也只能通过主线程来变化，所以说操作网络要开启一个子线程执行，而UI的改变则通过handler消息传递给主线程，委托主线程操作。