如何将图像动态添加到 GridView? [英] How can I dynamically add images to a GridView?

问题描述

我有一个基于项目数组创建的 GridView.当网格滚动到底部时，我需要添加更多图像，但我不知道该怎么做.

I have a GridView that is created based on an array of items. I need to add more images as the grid is scrolled to the bottom, but I'm not sure how to do that.

现在我明白了:

1. 我有一个适配器，它解析数组并向将返回 ImageViews
的类提供 ImageIds
2. 我必须以某种方式更改此数组并让适配器知道它，所以我的问题是，我如何获得对此适配器的引用?

这是我的代码:

package com.wm.grid;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListAdapter;
import android.widget.Toast;

public class GridActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final Integer[] mThumbIds12 = {
                R.drawable.sample_2, R.drawable.sample_3,R.drawable.s1,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_0, R.drawable.sample_1,
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_0, R.drawable.sample_1,
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7
    };
    final Integer[] mThumbIds1 = { 
            R.drawable.sample_2, R.drawable.sample_3,R.drawable.s1,
            R.drawable.sample_2, R.drawable.sample_3,R.drawable.s1,
            R.drawable.sample_2, R.drawable.sample_3,R.drawable.s1,
            R.drawable.sample_2, R.drawable.sample_3,R.drawable.s1,
    };
    final GridView gridview = (GridView) findViewById(R.id.gridview);
    gridview.setAdapter(new ImageAdapter(this,mThumbIds12));
    gridview.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
            Toast.makeText(GridActivity.this, "" + position, Toast.LENGTH_SHORT).show();

        }
    });
    gridview.setOnScrollListener(new OnScrollListener() {
        public void onScrollStateChanged(AbsListView view, int scrollState) {
            switch (scrollState) {
            case OnScrollListener.SCROLL_STATE_IDLE:
                //List is idle
                break;
            case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:
                //Toast.makeText(GridActivity.this, "X", Toast.LENGTH_SHORT).show();
                break;
            case OnScrollListener.SCROLL_STATE_FLING:
                //Toast.makeText(GridActivity.this, "Z", Toast.LENGTH_SHORT).show();
                break;
            }   
        }

        public void onScroll(AbsListView view, int firstVisibleItem,
                int visibleItemCount, int totalItemCount) {
            if(firstVisibleItem + visibleItemCount == totalItemCount){
                Toast.makeText(GridActivity.this, "BOTTOM", Toast.LENGTH_SHORT).show();

            }
            //Toast.makeText(GridActivity.this, "TOP", Toast.LENGTH_SHORT).show();  
        }
    });

}
}

现在有一些冗余代码，但这是我的测试项目.我所知道的是，适配器的更新必须在 firstVisibleItem + visibleItemCount == totalItemCount 时发生(即当 GridView 到达底部时).

Now there is some redundant code, but this is my testing project. All I know is that the updating of the adapter has to happen when firstVisibleItem + visibleItemCount == totalItemCount (i.e. when the GridView has reached the bottom).

这是我的 ImageAdapter(基于 Android 开发站点)

This is my ImageAdapter (based on the Android dev site)

package com.wm.grid;

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

import com.wm.grid.R;

public class ImageAdapter extends BaseAdapter {
   private Context mContext;
   private Integer[] mThumbIds;
    public ImageAdapter(Context c,Integer[] m) {
        mContext = c;
        mThumbIds = m;
    }

    public int getCount() {
        return mThumbIds.length;
    }

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

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

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {  // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
            imageView.setLayoutParams(new GridView.LayoutParams(150, 150));
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            imageView.setPadding(8, 8, 8, 8);
        } else {
            imageView = (ImageView) convertView;
        }

        imageView.setImageResource(mThumbIds[position]);
        return imageView;
    }
    public Integer[] AddItems(Integer[] a){
        final Integer[] aThumbIds;
        final int i;
        aThumbIds = a;
        Integer[] a2 = new Integer[mThumbIds.length + aThumbIds.length];
        System.arraycopy(mThumbIds, 0, a2, 0, mThumbIds.length);
        System.arraycopy(aThumbIds, 0, a2, mThumbIds.length, aThumbIds.length);
        return mThumbIds;
    }
}

图像.xml

<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
       android:id="@+id/grid_item_image"
      android:layout_width="50dp"
      android:layout_height="50dp"
      android:src="@drawable/s1"
      >
</ImageView>

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="@+id/layout1"
>
<LinearLayout
  android:orientation="horizontal"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:layout_weight="1">

<TextView
android:id="@+id/tv1"
android:layout_width="fill_parent"
android:layout_height="40pt"
android:text="row three"
android:textSize="15pt" />

</LinearLayout>
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1">
<GridView  
android:id="@+id/gridview"
android:layout_width="fill_parent" 
android:layout_height="fill_parent"
android:columnWidth="150dp"
android:numColumns="auto_fit"
android:verticalSpacing="2dp"
android:horizontalSpacing="2dp"
android:stretchMode="columnWidth"
android:gravity="center"
/>
</LinearLayout>
</LinearLayout>

我应该如何处理这个问题?

How should I approach this?

推荐答案

您可以通过 .getAdapter() 获取对支持 GridView 的适配器的引用.当用户向下滚动时，获取此适配器，添加新图像(我认为您应该使用 ArrayList 而不是简单数组，以便您可以轻松地在 ImageAdapter 类中附加更多数据)，并在现在修改的适配器上调用 .notifyDatasetChanged()，因此它将加载新数据.

You can get reference to the adapter backing the GridView by .getAdapter(). When the user scrolled down, get this adapter, add the new images (I think you should use an ArrayList instead of simple arrays so you can easily append more data in the ImageAdapter class), and call .notifyDatasetChanged() on the now modified adapter, so it'll load in the new data.

这篇关于如何将图像动态添加到 GridView?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！