ListView單條目刷新---界面跳轉

主要使用的是ListView單個條目重繪的思想

 ListView的每個條目都是一個View,那麼View就可以通過重繪來進行數據的刷新,那麼單個條目的刷新,主要是把兩點抓住,一個就是要進行數據改變的View,第二個就是View所在的position這兩點在界面跳轉的時候就非常重要,因爲要實現單條目刷新,那麼就要將要刷新的Item確定下來,但是ListView在加載的時候要進行緩存複用,那麼View必定就會被複用,那麼就要將每個條目的View 的引用進行存儲起來,當position在兩個界面直接進行傳遞的時候,就可以輕易的找到原先點擊的View,進行重繪操作 本例demo筆者並沒有用ListView的setOnItemClickListener方法,而是給每個item設置相應的監聽操作,方便數據的傳遞, setOnItemClickListener方法,讀者可以自己測試,以下給出相應的代碼,優化沒有做,因爲只是個小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 {
    //存儲測試數據標題
    private ArrayList<String> al;
//存儲計數器
    private ArrayList<String> cl;
//存儲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("測試數據" + 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);
                 //重繪
                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);
            //從view集合中獲取相應位置的view進行操作
            View view = vs.get(position);
            TextView countView = (TextView) view.findViewById(R.id.count);
            countView.setText(String.valueOf(newCount));
            //重繪view
            countView.invalidate();
            //用獲取到的數據進行集合更新
            String s = String.valueOf(newCount);
            cl.set(position, s);
            //Log.i("log", "改變後" + cl.toString());
        } else {
            Toast.makeText(MainActivity.this, "data爲空", Toast.LENGTH_SHORT).show();
        }
    }
}

MainActivity佈局和ListView的條目佈局

<?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="測試數據"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/count"
        android:textColor="#f00"
        android:text="計數器"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

點擊條目跳轉的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的佈局文件

<?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="計數器"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>