Android listview 增删改查代码实例

ListView

ListView可以用于展示列表数据,配合嵌入列表的控件,可以实现各种复杂的逻辑.
我查到的资料里对ListView的使用大部分是显示固定的列表,少有谈及ListView的动态
修改.这里大致总结下怎么动态增删改查列表备忘.

ListView类似于链表,每个单元对应一个view.
单元的创建需要Adapter,包含了单元的构造和事件的监听.
比如一个单元可能包括一个TextView和一个Button控件,
Adapter负责构造单元里的控件并监听控件的事件.

整合listview逻辑

从程序设计的角度来看,listview的操作最好是独立封装成一个类.
所以应该自定义adapter继承BaseAdapter.
Adapter完全可以抽象成ListView控件的proxy,对ListView的操作都
通过Adapter实现.

示例代码

1. 定义单元控件(xml描述)
   在工程中加入xml文件
    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

2. 定义adapter
public class PeerListAdapter extends BaseAdapter{
    private final String tag = "Online Peer list:";
    private ArrayList<String> mList;
    private Context mContext;
    private LayoutInflater mInflater;

    public PeerListAdapter(Context context) {
        super();
        mContext = context;//保存上下文(也就是对应的MainActivity)
        mInflater = LayoutInflater.from(mContext);
        mList = new ArrayList<String>();
        mList.add(tag);
        this.notifyDataSetChanged();
    }

    public void addPeer(String peer) {
        mList.add(peer);
        this.notifyDataSetChanged();
    }

    public void reset() {
        mList.clear();
    }

    @Override
    public View getView(final int i, View view, ViewGroup viewGroup) {
        if (view == null) {
            view = mInflater.inflate(R.layout.peerlist_view, null);
        }
        TextView textView = view.findViewById(R.id.text);
        textView.setText(mList.get(i));
        Button button = (Button)view.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String msg = mList.get(i);
                Log.d("sliver", msg);
                Toast.makeText(mContext, msg, Toast.LENGTH_SHORT);
            }
        });
        return view;
    }

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

    @Override
    public Object getItem(int i) {
        return null;
    }

    @Override
    public long getItemId(int i) {
        return 0;
    }

    @Nullable
    @Override
    public CharSequence[] getAutofillOptions() {
        return new CharSequence[0];
    }
}

3. activity中调用adapter
    refresh_button是自定义的按钮 用来触发添加单元到listview的动作
public class MainActivity extends AppCompatActivity implements View.OnClickListener{
    private ArrayList<String> mListData;
    private ListView mList;
    private PeerListAdapter mAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mAdapter = new PeerListAdapter(this);

        mList = (ListView)findViewById(R.id.peer_list);
        mList.setAdapter(mAdapter);

        Button refresh_bt = (Button)findViewById(R.id.refresh_button);
        refresh_bt.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        Log.d("sliver", "button on");
        mAdapter.addPeer("sliver");
    }
}