Android----------实现简单的购物车加减器

1.布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">

<Button
android:id="@+id/jian"
android:onClick="onClick"
android:clickable="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="-" />
<EditText
android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="1"/>
<Button
android:id="@+id/add"
android:onClick="onClick"
android:clickable="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="+" />
</LinearLayout>

2. 主界面

public class MainActivity extends AppCompatActivity {
private Button add,jian;
private TextView tv;
private int amount =0; //购买数量
// private int goods_storage = 1; //商品库存
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

add=(Button)findViewById(R.id.add);
jian=(Button)findViewById(R.id.jian);
tv=(TextView)findViewById(R.id.text);
add.setTag("+");
jian.setTag("-");
tv.setInputType(android.text.InputType.TYPE_CLASS_NUMBER);
tv.setText(String.valueOf(amount));
SetViewListener();

}

private void SetViewListener() {
add.setOnClickListener(new OnButtonClickListener());
jian.setOnClickListener(new OnButtonClickListener());
//  tv.setOnClickListener(new OnTextChangeListener());
}
class OnButtonClickListener implements View.OnClickListener{

@Override
public void onClick(View v) {
String s = tv.getText().toString();
if (s==null||s.equals("")){
amount=0;
tv.setText("0");
}else {
if (v.getTag().equals("+")){
if (++amount < 0){
//先加，再判断
amount--;
}else {
tv.setText(String.valueOf(amount));
}
}else if (v.getTag().equals("-")){
if (--amount < 0){
//先减，再判断
amount++;
}else {
tv.setText(String.valueOf(amount));
}

}
}

}
}

}