ListView单条目刷新---界面跳转

主要使用的是ListView单个条目重绘的思想

 ListView的每个条目都是一个View,那么View就可以通过重绘来进行数据的刷新,那么单个条目的刷新,主要是把两点抓住,一个就是要进行数据改变的View,第二个就是View所在的position这两点在界面跳转的时候就非常重要,因为要实现单条目刷新,那么就要将要刷新的Item确定下来,但是ListView在加载的时候要进行缓存复用,那么View必定就会被复用,那么就要将每个条目的View 的引用进行存储起来,当position在两个界面直接进行传递的时候,就可以轻易的找到原先点击的View,进行重绘操作 本例demo笔者并没有用ListView的setOnItemClickListener方法,而是给每个item设置相应的监听操作,方便数据的传递, setOnItemClickListener方法,读者可以自己测试,以下给出相应的代码,优化没有做,因为只是个小demo,主要是思想

MainActivity:

package cn.itcast.demo2;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    //存储测试数据标题
    private ArrayList<String> al;
//存储计数器
    private ArrayList<String> cl;
//存储item的View引用
    private ArrayList<View> vs = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        al = new ArrayList<>();
        for (int i = 0; i < 50; i++) {
            al.add("测试数据" + i);
        }
        cl = new ArrayList<>();
        for (int i = 0; i < 50; i++) {
            cl.add(i + "");
        }
        initView();
    }

    public void initView() {
        ListView lv = (ListView) findViewById(R.id.lv);
        lv.setAdapter(new BaseAdapter() {
            @Override
            public int getCount() {
                return al.size();
            }

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

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

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                //Log.i("log", "使用的" + cl.toString());
            if (convertView == null) {
            convertView = View.inflate(getApplicationContext(), R.layout.listview_item,null);
                }
                TextView test = (TextView) convertView.findViewById(R.id.testdata);
                String p = al.get(position);
                test.setText(p);
                TextView count = (TextView) convertView.findViewById(R.id.count);
                String c = cl.get(position);
                count.setText(c);
                clickListener = new MyClickListener(Integer.parseInt(c), position);
                vs.add(convertView);
                convertView.setOnClickListener(clickListener);
                 //重绘
                convertView.invalidate();
                return convertView;
            }
        });
    }

    MyClickListener clickListener;

    public class MyClickListener implements View.OnClickListener {
        int count;
        int position;

        public MyClickListener(int count, int position) {
            this.count = count;
            this.position = position;
        }

        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, CountActivity.class);
            intent.putExtra("count", count);
            intent.putExtra("position", position);
            startActivityForResult(intent, 0);
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (data != null) {
            int newCount = data.getIntExtra("count", 0);
            int position = data.getIntExtra("position", 0);
            //从view集合中获取相应位置的view进行操作
            View view = vs.get(position);
            TextView countView = (TextView) view.findViewById(R.id.count);
            countView.setText(String.valueOf(newCount));
            //重绘view
            countView.invalidate();
            //用获取到的数据进行集合更新
            String s = String.valueOf(newCount);
            cl.set(position, s);
            //Log.i("log", "改变后" + cl.toString());
        } else {
            Toast.makeText(MainActivity.this, "data为空", Toast.LENGTH_SHORT).show();
        }
    }
}

MainActivity布局和ListView的条目布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"></ListView>
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/testdata"
        android:textColor="@android:color/black"
        android:layout_width="wrap_content"
        android:text="测试数据"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/count"
        android:textColor="#f00"
        android:text="计数器"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

点击条目跳转的Activity—-CountActivity

package cn.itcast.demo2;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class CountActivity extends AppCompatActivity {

    private int count;
    private int position;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_count);
        Intent intent = getIntent();
        count = intent.getIntExtra("count" , 0);
        position = intent.getIntExtra("position", 0);
        final TextView mCount = (TextView) findViewById(R.id.tv_count);
        Button btn = (Button) findViewById(R.id.btn);
        mCount.setText(String.valueOf(count));
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                count++;
                mCount.setText(String.valueOf(count));
                mCount.invalidate();
            }
        });
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK){
            Intent intent = new Intent();
            intent.putExtra("position", position);
            intent.putExtra("count", count);
            setResult(0, intent);
            finish();
        }
        return super.onKeyDown(keyCode, event);
    }
}

CountActivity的布局文件

<?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="match_parent"
    android:orientation="vertical"
    >

    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="count++"
        />
    <TextView
        android:id="@+id/tv_count"
        android:textColor="@android:color/holo_red_dark"
        android:text="计数器"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>