在剛開是接觸Android學習各種控件,ListView絕對是比較難掌握的一個控件,但是ListView又是很重要的一個控件,這也就要求我們必須好好掌握,現(xiàn)在Android出了recyclerview控件,這個控件比ListView要強大,未來應該會逐漸代替ListView,現(xiàn)在學習ListView可能有點過時了,但是ListView還是有很多值得我們學習的.因為多學一點沒有壞處.
1.基本使用:展示數(shù)據(jù)和接收事件響應
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private ListView mListView;
private ArrayList<String> mList = new ArrayList<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mListView = (ListView) findViewById(R.id.container);
initData();
mListView.setAdapter(new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_dropdown_item_1line, mList));
mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(MainActivity.this, mList.get(position), Toast.LENGTH_SHORT).show();
}
});
}
private void initData() {
for (int i = 0; i < 20; i++) {
mList.add("this is item " + i);
}
}
}
效果圖:
2017-10-22 14-07-31屏幕截圖.png
2.常用屬性設置:
<ListView
android:id="@+id/container"
android:divider="@color/colorPrimary"http://定義分割線的背景顏色
android:dividerHeight="1dp"http://設置分割線的寬度
android:layout_height="match_parent"
android:layout_width="match_parent"/>
如果想取消分割線顯示:
setDividerHeight(0);// android:divider屬性設置為@null或者設置為透明顏色.當然還有一些其他屬性,和其他控件的屬性設置差不多.
3,展示數(shù)據(jù)之Adapter.
ArrayAdapter:用來展示單條字符串數(shù)據(jù),并且Android提供有現(xiàn)成的子布局,就是方便開發(fā)者展示數(shù)據(jù),上面就是具體用法.
SimpleAdapter:展示的數(shù)據(jù)比ArrayAdapter展示的數(shù)據(jù)要豐富,可以用來展示多條數(shù)據(jù),閱讀源碼發(fā)現(xiàn),展示的數(shù)據(jù)類型包括imageView,textVIew和checkBox,下面我們來展示這三種類型的數(shù)據(jù):
子布局:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:layout_margin="5dp"
android:id="@+id/image_view_item"
android:src="@drawable/icon_one"
android:scaleType="fitXY"
android:layout_width="40dp"
android:layout_height="40dp"/>
<TextView
android:layout_marginTop="5dp"
android:id="@+id/text_view_item"
android:layout_weight="1"
android:layout_height="wrap_content"
android:layout_width="0dp"/>
<CheckBox
android:layout_margin="5dp"
android:clickable="false" //為了防止 checkBox搶走item的點擊事件,根據(jù)實際情況來設置
android:focusable="false"
android:id="@+id/check_box_item"
android:layout_gravity="center_vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
代碼:
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private ListView mListView;
private ArrayList<HashMap<String, Object>> mList = new ArrayList<HashMap<String, Object>>();
private int[] mImages = new int[]{R.drawable.icon_one, R.drawable.icon_two, R.drawable.icon_three, R.drawable.icon_four};
private SimpleAdapter simpleAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mListView = (ListView) findViewById(R.id.container);
initData();
simpleAdapter = new SimpleAdapter(MainActivity.this, mList, R.layout.list_item,
new String[]{"image", "text", "check"}, new int[]{R.id.image_view_item, R.id.text_view_item, R.id.check_box_item});
mListView.setAdapter(simpleAdapter);
mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(MainActivity.this, mList.get(position).get("text").toString(), Toast.LENGTH_SHORT).show();
if (mList.get(position).get("check").equals(false)) {
((CheckBox) view.findViewById(R.id.check_box_item)).setChecked(true);
mList.get(position).put("check", true);
} else {
((CheckBox) view.findViewById(R.id.check_box_item)).setChecked(false);
mList.get(position).put("check", false);
}
simpleAdapter.notifyDataSetChanged();
}
});
}
private void initData() {
Random random = new Random();
for (int i = 0; i < 20; i++) {
HashMap<String, Object> map = new HashMap<String, Object>();
map.put("image", mImages[random.nextInt(mImages.length)]);
map.put("text", "this is item " + i);
map.put("check", random.nextBoolean());
mList.add(map);
}
}
}
效果圖:
2017-10-22 15-47-28屏幕截圖.png
BaseAdapter:以上幾個現(xiàn)成的Adapter是Android幫我們封裝實現(xiàn)好的Adapter,如果在實際開發(fā)中需要按照數(shù)據(jù)的組成來自定義布局,那么就需要實現(xiàn)自己的Adapter,自定義的Adapter都是需要繼承BaseAdapte.
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
private ListView mListView;
private ArrayList<Data> mList = new ArrayList<Data>();
private int[] mImages = new int[]{R.drawable.icon_one, R.drawable.icon_two, R.drawable.icon_three, R.drawable.icon_four};
private MyAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mListView = (ListView) findViewById(R.id.container);
initData();
mAdapter = new MyAdapter();
mListView.setAdapter(mAdapter);
mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Toast.makeText(MainActivity.this, mList.get(position).getmTitle(), Toast.LENGTH_SHORT).show();
if (!mList.get(position).ismIsCheck()) {
((CheckBox) view.findViewById(R.id.check_box_item)).setChecked(true);
mList.get(position).setmIsCheck(true);
} else {
((CheckBox) view.findViewById(R.id.check_box_item)).setChecked(false);
mList.get(position).setmIsCheck(false);
}
mAdapter.notifyDataSetChanged();
}
});
}
private void initData() {
Random random = new Random();
for (int i = 0; i < 20; i++) {
Data data = new Data();
data.setmImage_id(mImages[random.nextInt(mImages.length)]);
data.setmTitle("this is base adapter item" + i);
data.setmIsCheck(random.nextBoolean());
mList.add(data);
}
}
private class MyAdapter extends BaseAdapter{
@Override
public int getCount() {
return mList.size();
}
@Override
public Object getItem(int position) {
return mList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder = null;
if (convertView == null) {
convertView = LayoutInflater.from(MainActivity.this).inflate(R.layout.list_item, parent, false);
holder = new ViewHolder();
holder.imageView = (ImageView) convertView.findViewById(R.id.image_view_item);
holder.textView = (TextView) convertView.findViewById(R.id.text_view_item);
holder.checkBox = (CheckBox) convertView.findViewById(R.id.check_box_item);
convertView.setTag(holder);
} else {
holder = ((ViewHolder) convertView.getTag());
}
holder.imageView.setImageResource(mList.get(position).getmImage_id());
holder.textView.setText(mList.get(position).getmTitle());
holder.checkBox.setChecked(mList.get(position).ismIsCheck());
return convertView;
}
private class ViewHolder{
private ImageView imageView;
private TextView textView;
private CheckBox checkBox;
}
}
實現(xiàn)效果和上面用到的SimpleAdapter效果是一樣的,不同的是創(chuàng)建了一個javaBean對象用來封裝數(shù)據(jù),并且我們在自定義布局加載數(shù)據(jù)時,要充分用到緩存和viewHolder,優(yōu)化加載性能,這是固定寫法,當然在性能考慮方法,如果布局中加載的圖片過大,需要對圖片資源做單獨的優(yōu)化處理,這是屬于對圖片的優(yōu)化,這個話題另外再說,其實剛剛用到的ArrayAdapter是一個泛型類,我們只要改變傳入的數(shù)據(jù)集和重寫getView方法,可以很方便的實現(xiàn)自定義,不用重寫這個BaseAdapter的抽象方法,并且ArrayAdapter還提供類其他方法,比如增加數(shù)據(jù),更新數(shù)據(jù)的方法,還是比較好用的.好了,以上就是ListView的常規(guī)用法.
wolf-2864647__340.jpg
