动态添加和删除ListView

这是xml布局文件，两个按钮一个增加一个减少item，下面是一个listview

方法如下，原理是向adapter的集合添加数据，调用NotifyDataSetChanged会强制刷新界面，这里面涉及到java的观察者模式和反射机制。

package demo.jim.com.addlistview.testlistview;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import demo.jim.com.addlistview.R;

public class MainActivity extends Activity implements View.OnClickListener {

    private Button addBtn;
    private Button removeBtn;
    private ListView show;
    private MyAdapter myAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initUI();

        myAdapter = new MyAdapter(this);
        show.setAdapter(myAdapter);
    }

    private void initUI() {
        addBtn = (Button) findViewById(R.id.btn_add);
        removeBtn = (Button) findViewById(R.id.btn_remove);
        show = (ListView) findViewById(R.id.lv_show);
        addBtn.setOnClickListener(this);
        removeBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btn_add:
                myAdapter.list.add("345");
                myAdapter.notifyDataSetChanged();
                break;
            case R.id.btn_remove:
                //判断item的数量否则会出错
                if (myAdapter.getCount() > 0) {
                    myAdapter.list.remove(0);
                    //动态改变显示的关键，刷新界面的item
                    myAdapter.notifyDataSetChanged();
                } else {
                    //删除到最后一个时用Toast提示
                    Toast.makeText(MainActivity.this, "没有联系人了", Toast.LENGTH_SHORT).show();
                }
                break;

        }
    }
}

适配器的代码如下，通过list集合控制item数量，默认加载3个item

package demo.jim.com.addlistview.testlistview;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import java.util.ArrayList;

import demo.jim.com.addlistview.R;

/**
 * Created by huangjim on 7/20/2015.
 */
public class MyAdapter extends BaseAdapter {
    public ArrayList list;
    private Context context;

    public MyAdapter(Context _Context) {
        this.context = _Context;
        list = new ArrayList();

        //默认加载3个item
        for (int i = 0; i < 3; i++) {
            list.add("345");
        }
    }

    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(R.layout.activity_list_item1, null);
        }
        return convertView;
    }
}

效果图：