<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:textSize="20sp"
android:textColor="#0000FF"
android:text="@string/photos" />
<ListView
android:id="@+id/listView"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/textView"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
</RelativeLayout>
每一個項目(item)的選項內容
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView android:id="@+id/imageView"
android:layout_width="48dp"
android:layout_height="48dp"
android:contentDescription="@string/img_desc"
android:padding="6dp" />
<TextView android:id="@+id/textView"
android:layout_gravity="center_vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:padding="6dp" />
</LinearLayout>
package com.lcpan.listview;
import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private ListView listView;
//A view that shows items in a vertically scrolling list. The items come from the ListAdapter associated with this view.
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViews();//因為現在程式碼很大了，所以寫在方法裡，呼叫方法
}
private void findViews() {
listView = (ListView) findViewById(R.id.listView);
listView.setAdapter(new MyAdapter(MainActivity.this)); //把MyAdapter指定給ListView元件
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,int position, long id) {//
// 選定某個選項（item）時會呼叫此方法
// view代表被點選的元件,在此為listview_item.xml的LinearLayout元件(也可以說就是整個listview_item.xml)
TextView textView = (TextView) ((LinearLayout) view).getChildAt(1);
//指listview_item.xml的LinearLayout元件中的第二個元素TextView android:id="@+id/textView"
Toast.makeText(getApplicationContext(), textView.getText(),
Toast.LENGTH_SHORT).show();//出現彈跳視窗
}
});
}
private class MyAdapter extends BaseAdapter {//由於繼承BaseAdapter，所以得覆寫四種方法
//Adapter是一個轉接器，接收資料、丟出資料
private LayoutInflater layoutInflater;//Inflater：解壓縮、產生器
private Integer[] images = {//把圖片放入陣列中
R.drawable.p01, R.drawable.p02, R.drawable.p03, R.drawable.p04,
R.drawable.p05, R.drawable.p06, R.drawable.p07, R.drawable.p08,
R.drawable.p09, R.drawable.p10, R.drawable.p11, R.drawable.p12
};
public MyAdapter(Context context) {//建構子，建立一個layout物件
layoutInflater =
(LayoutInflater) context.getSystemService(LAYOUT_INFLATER_SERVICE);
}
private class ViewHolder {
ImageView imageView;
TextView textView;
}
@Override //取得資料數量(12張照片)，也就是內容有多少個item
public int getCount() {
return images.length;
}
@Override //???不用動，position從0開始
public Object getItem(int position) {
return position;
}
@Override //???不用動
public long getItemId(int position) {
return position;
}
@Override //系統互依據getCount()的回傳值決定呼叫此方法的次數，第一次呼叫時position=0，第二次=1
//每回呼叫getView都要配置好每個item的內容，應該類似迴圈
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder;//ViewHolder是自己寫的方法
// convertView為上次呼叫getView()所取得的View，指的是listView元件每個item的layout物件
if (convertView == null) {// 若convertView已存在,就無需再呼叫inflate()(解壓縮)重新產生它
convertView = layoutInflater.inflate(R.layout.listview_item, null);//null→預設最外層的layout
// inflate(int resource, ViewGroup root)
// Inflate a new view hierarchy from the specified xml resource.
//指定listview_item以產生convertView
viewHolder = new ViewHolder();
viewHolder.textView = (TextView) convertView.findViewById(R.id.textView);
viewHolder.imageView = (ImageView) convertView.findViewById(R.id.imageView);
// 利用setTag()將convertView和viewHolder建立View元件之間的階層關聯
// convertView為父元件,而viewHolder為子元件
convertView.setTag(viewHolder);//把viewHolder跟convertView綁在一起
} else {
viewHolder = (ViewHolder) convertView.getTag();//取出之前放在裡面的東西
}
viewHolder.imageView.setImageResource(images[position]);
viewHolder.textView.setText("image " + (position + 1));
return convertView;
}
} // end of class MyAdapter
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
【前端網頁開發技術】 (4)
