原文鏈接:http://www.cnblogs.com/qingblog/archive/2012/07/03/2575140.html
View中的setTag(Onbect)表示給View添加一個格外的數據,以後可以用getTag()將這個數據取出來。
可以用在多個Button添加一個監聽器,每個Button都設置不同的setTag。這個監聽器就通過getTag來分辨是哪個Button 被按下。
- import android.app.Activity;
- import android.os.Bundle;
- import android.view.View;
- import android.widget.Button;
- public class Main extends Activity {
- @Override
- public void onCreate(Bundle savedInstanceState){
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- Button button1 = (Button) findViewById(R.id.Button01);
- Button button2 = (Button) findViewById(R.id.Button02);
- Button button3 = (Button) findViewById(R.id.Button03);
- Button button4 = (Button) findViewById(R.id.Button04);
- MyListener listener = new MyListener();
- button1.setTag(1);
- button1.setOnClickListener(listener);
- button2.setTag(2);
- button2.setOnClickListener(listener);
- button3.setTag(3);
- button3.setOnClickListener(listener);
- button4.setTag(4);
- button4.setOnClickListener(listener);
- }
- public class MyListener implements View.OnClickListener {
- @Override
- public void onClick(View v) {
- int tag = (Integer) v.getTag();
- switch (tag){
- case 1:
- System.out.println("button1 click");
- break;
- case 2:
- System.out.println("button2 click");
- break;
- case 3:
- System.out.println("button3 click");
- break;
- case 4:
- System.out.println("button4 click");
- break;
- }
- }
- }
- }
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
public class Main extends Activity {
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button button1 = (Button) findViewById(R.id.Button01);
Button button2 = (Button) findViewById(R.id.Button02);
Button button3 = (Button) findViewById(R.id.Button03);
Button button4 = (Button) findViewById(R.id.Button04);
MyListener listener = new MyListener();
button1.setTag(1);
button1.setOnClickListener(listener);
button2.setTag(2);
button2.setOnClickListener(listener);
button3.setTag(3);
button3.setOnClickListener(listener);
button4.setTag(4);
button4.setOnClickListener(listener);
}
public class MyListener implements View.OnClickListener {
@Override
public void onClick(View v) {
int tag = (Integer) v.getTag();
switch (tag){
case 1:
System.out.println("button1 click");
break;
case 2:
System.out.println("button2 click");
break;
case 3:
System.out.println("button3 click");
break;
case 4:
System.out.println("button4 click");
break;
}
}
}
}
在寫listView 時候要重寫BaseAdapter
需要在每個item都加上button 點擊button做相應操作
這個時候需要button裏面設置下 這行的屬性button.setTag(item.user.name);
然後處理button事件。
這個東西在一些需要用到Adapter自定控件顯示方式的時候非常有用
Adapter 有個getView方法,可以使用setTag把查找的view緩存起來方便多次重用
- public View getView(int position, View convertView, ViewGroup parent) {
- ViewHolder vh;
- if (convertView == null){
- LayoutInflater inflater = (LayoutInflater) mWidgetsSwitchApp .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
- convertView = inflater.inflate(R.layout.app_gallery_item, null);
- vh = new ViewHolder();
- vh.view1 = (ImageView) convertView.findViewById(R.id.view1);
- vh.view2 = (ImageView) convertView.findViewById(R.id.view2);
- vh.view3= (ImageView) convertView.findViewById(R.id.view3);
- vh.view4 = (ImageView) convertView.findViewById(R.id.view4);
- convertView.setTag(vh);
- }else{
- vh = (ViewHolder) convertView.getTag();
- }
- //其他的代碼可以直接使用 vh.view1、vh.view2、vh.view3 、vh.view4
- }
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder vh;
if (convertView == null){
LayoutInflater inflater = (LayoutInflater) mWidgetsSwitchApp .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.app_gallery_item, null);
vh = new ViewHolder();
vh.view1 = (ImageView) convertView.findViewById(R.id.view1);
vh.view2 = (ImageView) convertView.findViewById(R.id.view2);
vh.view3= (ImageView) convertView.findViewById(R.id.view3);
vh.view4 = (ImageView) convertView.findViewById(R.id.view4);
convertView.setTag(vh);
}else{
vh = (ViewHolder) convertView.getTag();
}
//其他的代碼可以直接使用 vh.view1、vh.view2、vh.view3 、vh.view4
}
你可以看看android的源碼,特別有listview的,你就會發現這個函數很多時候有妙用!呵呵!
我的一點理解是,綁定數據,特別是綁定數據到view。而且可以用getTag()取得,很方便,而且是任意類型的數據,真的很酷。
在實例BaseAdapter()的getView(position, convertView, par)裏有用到。convertView這裏會用到setTag() getTag()。就可以生成convertView並複用裏面的widget
一直覺得這個東西沒啥用setTag(),不過只要能用上 就是比較巧的了
在一個程序中呢 我有好多個button 我想點擊一個出現1 點擊第二個出現2
- for (int i = 0; i < 20; i++) {
- cells[i] = (ImageView) findViewById(cellIDs[i]);
- cells[cellnumber++].setOnClickListener(new OnClickListener() {
- public void onClick(View v){
- cellClicked(cellnumber, v);
- }
- });
- }
for (int i = 0; i < 20; i++) {
cells[i] = (ImageView) findViewById(cellIDs[i]);
cells[cellnumber++].setOnClickListener(new OnClickListener() {
public void onClick(View v){
cellClicked(cellnumber, v);
}
});
}
上面的代碼效率不高 而且 無論點擊哪一個都會出現21 當然這是我邏輯錯誤那怎麼實現呢
- OnClickListener listener = new OnClickListener() {
- public void onClick(View v){
- int cellId = (Integer) v.getTag(); cellClicked(cellId, v);
- }
- }
- View v;
- for (int i = 0; i < 20; i++){
- v = findViewById(cellIDs[i]);
- v.setOnClickListener(listener);
- v.setTag(i);
- }
OnClickListener listener = new OnClickListener() {
public void onClick(View v){
int cellId = (Integer) v.getTag(); cellClicked(cellId, v);
}
}
View v;
for (int i = 0; i < 20; i++){
v = findViewById(cellIDs[i]);
v.setOnClickListener(listener);
v.setTag(i);
}
這樣呢就實例話一個listener,同時通過tag傳值就不是每一個實例都做了