android.os.NetworkOnMainThreadException,Android根据图片URL加载图片

本文介绍如何在Android应用中避免主线程进行网络操作导致的异常,通过使用AsyncTask实现从网络下载图片并显示在ImageView组件上的过程。

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当在主线程中执行网络操作时,比如根据图片URL加载图片,会抛出NetworkOnMainThreadException这个异常。

那么怎么从网络断获取图片并加载呢?使用AsyncTask:

json字符串:

{
    "people": [ //数组,最像的50个人,按分数的降序排列
        {
            "score": 0.63, //浮点数,相似度,0到1,越接近1越像
            "id": 732, //字符串,这个人的id
            "chinese_name": "刘博" //字符串,这个人的中文名字。可能是空字符串。chinese_name和english_name至少有一个非空
            "english_name": "Barack_Obama" //字符串,这个人的英文名字。可能是空字符串。chinese_name和english_name至少有一个非空
        },
        {}, ...
    ],
    "final_time": 877 //整数,服务器完整处理过程所用时间
}
获取图片URL:

JSONObject jsonObject = JSON.parseObject(json);
            JSONArray peopleJsonArr = jsonObject.getJSONArray("people");
            JSONObject peopleJsonObj = peopleJsonArr.getJSONObject(0);
            final String PEOPLEID = peopleJsonObj.getString("id");
            Log.e("PEOPLEID====",PEOPLEID);
            String peolepUrl = "http://faceall.cn/static/img/celebrity/"+PEOPLEID+".jpg";//图片的URL
            new LoadBitmapFromUrl().execute(peolepUrl);//加载图片
private class LoadBitmapFromUrl extends AsyncTask<String,Void,Bitmap>{
        @Override
        protected Bitmap doInBackground(String... params) {
            return loadImageFromNetwork(params[0]);
        }
        @Override
        protected void onPostExecute(Bitmap bitmap) {
            ivResultCelebrity.setImageBitmap(bitmap);//要加载的图片
        }
}

private Bitmap loadImageFromNetwork(String url) {
        //得到可用的图片
        Bitmap bitmap = simpleNetworkImage(url);
        if (bitmap == null) {
            Log.i("loadImageFromNetwork:", "bitmap is null");
        }
        return bitmap;
}

public Bitmap simpleNetworkImage(String url) {
        Bitmap imgBitmap = null;
        try {
            URL picUrl = new URL(url);
            imgBitmap = BitmapFactory.decodeStream(picUrl.openStream());
        } catch (IOException e) {
            e.printStackTrace();
        }
        return imgBitmap;
}







我做了一个安卓画板app现在添加了一个从url下载图片并设置成画板背板的功能。我把代码给你看,在我输入了https://www.nottingham.edu.cn/image-library/campus-news/signofnottingham.jpg的网站后提示下载失败 /* * Copyright (C) 2007 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package cn.edu.nottingham.jianxingwang.fingerpainter; import android.content.ContentResolver; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Path; import android.net.Uri; import android.os.Bundle; import android.os.Parcelable; import android.util.AttributeSet; import android.util.Log; import android.view.MotionEvent; import android.view.View; import android.widget.Button; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.util.Stack; /** * Created by pszmdf on 13/10/16. * * Derived from android graphics API sample com.example.android.apis.graphics.Fingerpaint * android.googlesource.com/platform/development/+/master/samples/ApiDemos/src/com/example/android/apis/graphics/FingerPaint.java * */ public class FingerPainterView extends View { private Context context; private Canvas canvas; private Paint paint; private Bitmap bitmap; private Path path; private Uri uri; private Stack<Bitmap> undoStack = new
最新发布
03-29
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