Android gallery画廊

1.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<Gallery
android:id="@+id/gallery"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="30dp" >
</Gallery>

<ImageView
android:id="@+id/imageView"
android:layout_width="300dp"
android:layout_height="300dp"
android:layout_gravity="center_horizontal"
android:scaleType="fitCenter" />

</LinearLayout>

2.attrs.xml自定义属性文件：

<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="Gallery">
<attr name="android:galleryItemBackground"></attr>
</declare-styleable>
</resources>

3.java代码，通过适配器将图片放入gallery中显示并添加监听事件：

package com.android.mygallery;

import android.app.Activity;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.Toast;

public class Main extends Activity {
/** Called when the activity is first created. */
private Gallery gallery;
private ImageAdapter imageAdapter;
private ImageView imageView;
// 声明图片的数组
private int[] resIds = { R.drawable.item1, R.drawable.item2,
R.drawable.item3, R.drawable.item4, R.drawable.item5,
R.drawable.item6, R.drawable.item7, R.drawable.item8,
R.drawable.item9, R.drawable.item10, R.drawable.item11,
R.drawable.item12, R.drawable.item13, R.drawable.item14,
R.drawable.item15 };

// android的适配器
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
gallery = (Gallery) this.findViewById(R.id.gallery);
imageView = (ImageView) findViewById(R.id.imageView);
imageAdapter = new ImageAdapter(this);
gallery.setAdapter(imageAdapter);
//给画廊设置监听事件
gallery.setOnItemClickListener(new OnItemClickListener() {

@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// TODO Auto-generated method stub
//				Toast.makeText(Main.this, "" + position,
//                        Toast.LENGTH_LONG).show();
//				imageView.setImageResource(resIds[position%resIds.length]);
//				imageView.setBackgroundResource((int) id);
}
});
gallery.setOnItemSelectedListener(new OnItemSelectedListener() {

@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
// TODO Auto-generated method stub
imageView.setImageResource(resIds[position%resIds.length]);
}

@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub

}
});
}

public class ImageAdapter extends BaseAdapter {

private Context context;
int mGralleyItemBackground;// 使用简单的计数器，填充背景图片

public ImageAdapter(Context context) {
this.context = context;
// 读取属性
TypedArray typedArray = obtainStyledAttributes(R.styleable.Gallery);
mGralleyItemBackground = typedArray.getResourceId(
R.styleable.Gallery_android_galleryItemBackground, 5);

}

@Override
public int getCount() {
// TODO Auto-generated method stub
return Integer.MAX_VALUE;
}

@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return resIds[position];
}

@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
// 自定义的适配器，需要用自定义的布局来显示，通常android的通用布局是不能满足我们的需求
// 可以手工创建一个View视图，也可以inflate填充一个XML
// 从数据源中根据position 获得每一个Item的值，填充到指定的XML布局中
// View convertView 是一个旧的布局，如果没有新的布局填充的时候，将使用旧的布局
// 当前的布局，会被追加到父布局中
ImageView imageView = new ImageView(context);
imageView.setImageResource(resIds[position % resIds.length]);
imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
imageView.setLayoutParams(new Gallery.LayoutParams(200, 150));
imageView.setBackgroundResource(mGralleyItemBackground);
return imageView;
}

}
}

4.问题？：

①自定义属性是如何在java代码中使用的？

②typedArray.getResourceId(R.styleable.Gallery_android_galleryItemBackground, 5); 的返回值是什么？5是defaultValue，之前并没有对galleryItemBackground赋值，所以其返回值是什么？从哪里来？

③setBackgroundResource() 与setImageResource()的区别？

setBackgroundResource是从类 android.view.View 继承的方法






setImageResource








它們的原型如下：

void android.widget.ImageView.setImageResource(int
resId)

void android.view.View.setBackgroundResource(int resid)

區別是：

setImageResource與xml中的src的屬性才是相匹配的，而setBackgroundResource是與xml中的background屬性相匹配的。



④适配器的使用？