Question

我有一个应用程序在GridView中显示来自互联网的图像但是当运行时显示空活动并且没有显示图像

为什么活动不能获得图像？

。

这可能是我将其复制到网站上的代码，但它在网站上成功运行

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中

    <?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

它不起作用，因为图像无法立即从互联网上加载，您必须使用AsynkTask从互联网下载它们，然后您可以将它们添加到GridView。有些库可以为您see this one for example或this one执行所有这些操作。

在GridView上加载URL图像

1 个答案: