如何从Web服务显示图像？

Question

我想从URL中获取图像，但整个代码都很干净，但我没有输出。我该怎么办。

我使用了此网址中的全部代码

http://www.sanktips.com/2017/10/15/how-to-fetch-images-from-server-to-image-slider-with-viewpager-in-android-studio/#comment-43

这就是我得到的错误。

  

com.android.volley.ParseError：org.json.JSONException：java.lang.String类型的值无法转换为JSONArray

This is the mainactivity

    package com.example.admin.serverslider;

import android.support.v4.content.ContextCompat;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ImageView;
import android.widget.LinearLayout;

import com.android.volley.DefaultRetryPolicy;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;
import java.util.List;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity {

    ViewPager viewPager;
    LinearLayout sliderDotspanel;
    private int dotscount;
    private ImageView[] dots;

    RequestQueue rq;
    List<SliderUtils> sliderImg;
    ViewPagerAdapter viewPagerAdapter;

    /* String request_url = "http://localhost/sliderjsonoutput.php";*/
    String request_url = "http://georeachtech.com/missing.org/fetch_home_page_data.php";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        rq = CustomVolleyRequest.getInstance(this).getRequestQueue();
        rq = Volley.newRequestQueue(this);

        sliderImg = new ArrayList<>();

        viewPager = (ViewPager) findViewById(R.id.viewPager);

        sliderDotspanel = (LinearLayout) findViewById(R.id.SliderDots);

        sendRequest();


        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {

                for (int i = 0; i < dotscount; i++) {
                    dots[i].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.nonactivate));
                }

                dots[position].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.activate));

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });


    }


    public void sendRequest() {

        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET, request_url, null, new Response.Listener<JSONArray>() {


            @Override
            public void onResponse(JSONArray response) {
                for (int i = 0; i < response.length(); i++) {
                    SliderUtils sliderUtils = new SliderUtils();
                    try {
                        JSONObject jsonObject = response.getJSONObject(i);
                        //  sliderUtils.setSliderImageUrl(jsonObject.getString("id"));
                        sliderUtils.setSliderImageUrl(jsonObject.getString("image"));
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                    sliderImg.add(sliderUtils);
                }
                viewPagerAdapter = new ViewPagerAdapter(sliderImg, MainActivity.this);

                viewPager.setAdapter(viewPagerAdapter);

                dotscount = viewPagerAdapter.getCount();
                dots = new ImageView[dotscount];

                for (int i = 0; i < dotscount; i++) {

                    dots[i] = new ImageView(MainActivity.this);
                    dots[i].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.nonactivate));

                    LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);

                    params.setMargins(8, 0, 8, 0);

                    sliderDotspanel.addView(dots[i], params);

                }

                dots[0].setImageDrawable(ContextCompat.getDrawable(getApplicationContext(), R.drawable.activate));
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e("error", error.toString());

            }
        });
        rq.add(jsonArrayRequest);
        CustomVolleyRequest.getInstance(this).addToRequestQueue(jsonArrayRequest);
    }
}






    **This the custom volly class:**








import android.content.Context;
import android.graphics.Bitmap;
import android.util.LruCache;

import com.android.volley.Cache;
import com.android.volley.Network;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.BasicNetwork;
import com.android.volley.toolbox.DiskBasedCache;
import com.android.volley.toolbox.HurlStack;
import com.android.volley.toolbox.ImageLoader;



public class CustomVolleyRequest {
    private static CustomVolleyRequest customVolleyRequest;
    private static Context context;
    private RequestQueue requestQueue;
    private ImageLoader imageLoader;

    private CustomVolleyRequest(Context context){

        this.context = context;
        this.requestQueue = getRequestQueue();

        imageLoader = new ImageLoader(requestQueue, new ImageLoader.ImageCache() {

            private final LruCache<String, Bitmap> cache = new LruCache<String, Bitmap>(20);

            @Override
            public Bitmap getBitmap(String url) {
                return cache.get(url);
            }

            @Override
            public void putBitmap(String url, Bitmap bitmap) {
                cache.put(url, bitmap);
            }
        });

    }

    public static synchronized CustomVolleyRequest getInstance(Context context){

        if(customVolleyRequest == null){
            customVolleyRequest = new CustomVolleyRequest(context);
        }
        return customVolleyRequest;
    }

    public RequestQueue getRequestQueue(){

        if(requestQueue == null){

            Cache cache = new DiskBasedCache(context.getCacheDir(), 10 * 1024 * 1024);
            Network network = new BasicNetwork(new HurlStack());
            requestQueue = new RequestQueue(cache, network);
            requestQueue.start();

        }
        return requestQueue;
    }

    public  void addToRequestQueue(Request req) {
        getRequestQueue().add(req);
    }

    public ImageLoader getImageLoader(){

        return imageLoader;

    }


}

这是适配器类

package com.example.admin.serverslider;

import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.Toast;

import com.android.volley.toolbox.ImageLoader;

import java.util.List;

/**
 * Created by admin on 12/19/2017.
 */

public class ViewPagerAdapter  extends PagerAdapter {
    private Context context;
    private LayoutInflater layoutInflater;
    private List<SliderUtils> sliderImg;
    private ImageLoader imageLoader;


    public ViewPagerAdapter(List sliderImg,Context context) {
        this.sliderImg = sliderImg;
        this.context = context;
    }

    @Override
    public int getCount() {
        return sliderImg.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, final int position) {

        layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View view = layoutInflater.inflate(R.layout.custom_layout, null);

        SliderUtils utils = sliderImg.get(position);

        ImageView imageView = (ImageView) view.findViewById(R.id.imageView);

        imageLoader = CustomVolleyRequest.getInstance(context).getImageLoader();
        imageLoader.get(utils.getSliderImageUrl(), ImageLoader.getImageListener(imageView, R.mipmap.ic_launcher, android.R.drawable.ic_dialog_alert));


        view.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if(position == 0){
                    Toast.makeText(context, "Slide 1 Clicked", Toast.LENGTH_SHORT).show();
                } else if(position == 1){
                    Toast.makeText(context, "Slide 2 Clicked", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(context, "Slide 3 Clicked", Toast.LENGTH_SHORT).show();
                }

            }
        });

        ViewPager vp = (ViewPager) container;
        vp.addView(view, 0);
        return view;

    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {

        ViewPager vp = (ViewPager) container;
        View view = (View) object;
        vp.removeView(view);

    }
}

Answer 1

该链接看起来有效且有效，因此可能性

• 您没有正确的互联网权限

在这种情况下，在menifest文件中添加以下内容;

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

或

• 您确实拥有互联网权限，手机无法连接。您是否可以在设备上浏览互联网上的任何其他内容？如果模拟器尝试重新启动或重新创建设备。

Answer 2

request = new JsonArrayRequest(request_url, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {

                JSONObject jsonObject  = null ;

                for (int i = 0 ; i < response.length(); i++ ) {



                    SliderUtils sliderUtils = new SliderUtils();

                    try {
                          jsonObject = response.getJSONObject(i);

                          sliderUtils.setSliderImageUrl(jsonObject.getString("image1"));


                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                    sliderImg.add(sliderUtils);

                }