在GridView上加载URL图像

Question

I have an app show images from internet in GridView but when run that is showed an empty activity and didn't showed the images

why activity not get images ????????????

this may code I copied it form a website but it run successfully on the site

MainActivity.java

    package com.osman.gridviewnew;

import java.net.URL;
import java.util.ArrayList;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.widget.GridView;

public class MainActivity extends Activity {

     private GridView imageGrid;
     private ArrayList<Bitmap> bitmapList;

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

        this.imageGrid = (GridView) findViewById(R.id.gridview);
        this.bitmapList = new ArrayList<Bitmap>();

        try {
            for(int i = 0; i < 10; i++) {
                this.bitmapList.add(urlImageToBitmap("http://placehold.it/150x150"));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        this.imageGrid.setAdapter(new ImageAdapter(this, this.bitmapList));

    }

    private Bitmap urlImageToBitmap(String imageUrl) throws Exception {
        Bitmap result = null;
        URL url = new URL(imageUrl);
        if(url != null) {
            result = BitmapFactory.decodeStream(url.openConnection().getInputStream());
        }
        return result;
    }

}

ImageAdapter.java

    package com.osman.gridviewnew;

import java.util.ArrayList;

import android.content.Context;
import android.graphics.Bitmap;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class ImageAdapter extends BaseAdapter {

    private Context context;
    private ArrayList<Bitmap> bitmapList;

    public ImageAdapter(Context context, ArrayList<Bitmap> bitmapList) {
        this.context = context;
        this.bitmapList = bitmapList;
    }

    public int getCount() {
        return this.bitmapList.size();
    }

    public Object getItem(int position) {
        return null;
    }

    public long getItemId(int position) {
        return 0;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {
            imageView = new ImageView(this.context);
            imageView.setLayoutParams(new GridView.LayoutParams(115, 115));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        } else {
            imageView = (ImageView) convertView;
        }

        imageView.setImageBitmap(this.bitmapList.get(position));
        return imageView;
    }

}

main.xml

    <?xml version="1.0" encoding="utf-8"?>
<GridView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/gridview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:columnWidth="115dp"
    android:numColumns="auto_fit"
    android:verticalSpacing="5dp"
    android:horizontalSpacing="5dp"
    android:stretchMode="columnWidth"
    android:gravity="center" />

Answer 1

It doesn't work because Images don't get loaded instantly from the internet you have to use an AsynkTask to download them from the internet then you can add them to the GridView. There are libraries that does all this for you see this one for example or this one .