Android开发学习之路--UI之简单聊天界面

    学了很多的ui的知识，这里就来实现个聊天的界面，首先来实现个layout的xml，代码如下：

<?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">

    <ListView
        android:id="@+id/msg_list_view"
        android:layout_height="0dp"
        android:layout_width="match_parent"
        android:layout_weight="1"
        android:divider="#0000"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:id="@+id/input_text"
            android:layout_height="wrap_content"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:hint="输入你想说的话"
            android:maxLines="2"/>
        <Button
            android:id="@+id/send"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:text="发送"/>

    </LinearLayout>

</LinearLayout>

    这里主要是listview来实现聊天的记录显示，edittext用于输入信息，button用于按钮发送。效果如下：

    然后实现个listView的界面，这里用到了两张准备好的图片，是*.9.png，也就是9宫格的图片，主要的作用就是为了防止不该拉伸的地方拉伸，这里的界面用到了气泡，所以只要拉伸中间的背景就好了，两边的就不要拉伸了，新建msg_item.xml，代码如下：

<?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"
    android:padding="10dp">

    <LinearLayout
        android:id="@+id/left_layout"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_gravity="left"
        android:background="@drawable/left_messages">

        <TextView
            android:id="@+id/left_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="10dp"
            android:textColor="#fff"/>

    </LinearLayout>

    <LinearLayout
        android:id="@+id/right_layout"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_gravity="right"
        android:background="@drawable/right_messages">

        <TextView
            android:id="@+id/right_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="10dp"/>

    </LinearLayout>

</LinearLayout>

    效果如下图所示：

    这里的图片是网上找的png，然后ps改变大小，最后在android studio中，右击选择新建9-patch图片，然后选择拉伸的位置，如下图所示：

    这样，绿色显示的是整个背景图片，然后中间的红色就是可以拉伸的地方。其中相对于png图片，*.9.png图片主要多了四周的黑线条。这里不再详细讲解*.9.png图片的制作了。

    接着新建Msg类，代码如下：

package com.example.jared.uitest;

/**
 * Created by jared on 16/2/10.
 */
public class Msg {
    public static final int TYPE_RECEIVED = 0;
    public static final int TYPE_SEND = 1;

    private String content;
    private int type;

    public Msg(String content, int type) {
        this.content = content;
        this.type = type;
    }

    public String getContent() {
        return content;
    }

    public int getType() {
        return type;
    }
}

    然后就是Adapter了，MsgAdapter代码如下：

package com.example.jared.uitest;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.util.List;

/**
 * Created by jared on 16/2/10.
 */
public class MsgAdapter extends ArrayAdapter<Msg> {
    private int resourceId;

    public MsgAdapter(Context context, int textViewResourceId, List<Msg> objects) {
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        Msg msg = getItem(position);
        View view;
        ViewHolder viewHolder;
        if(convertView == null) {
            view = LayoutInflater.from(getContext()).inflate(resourceId, null);
            viewHolder = new ViewHolder();
            viewHolder.leftLayout = (LinearLayout)view.findViewById(R.id.left_layout);
            viewHolder.rightLayout = (LinearLayout)view.findViewById(R.id.right_layout);
            viewHolder.leftMsg = (TextView)view.findViewById(R.id.left_msg);
            viewHolder.rightMsg = (TextView)view.findViewById(R.id.right_msg);
            view.setTag(viewHolder);
        } else {
            view = convertView;
            viewHolder = (ViewHolder) view.getTag();
        }
        if(msg.getType() == Msg.TYPE_RECEIVED) {
            viewHolder.leftLayout.setVisibility(View.VISIBLE);
            viewHolder.rightLayout.setVisibility(View.GONE);
            viewHolder.leftMsg.setText(msg.getContent());
        } else if(msg.getType() == Msg.TYPE_SEND) {
            viewHolder.rightLayout.setVisibility(View.VISIBLE);
            viewHolder.leftLayout.setVisibility(View.GONE);
            viewHolder.rightMsg.setText(msg.getContent());
        }
        return view;
    }

    class ViewHolder {
        LinearLayout leftLayout;
        LinearLayout rightLayout;
        TextView leftMsg;
        TextView rightMsg;
    }
}

    最后我们来实现MainActivity的代码：

package com.example.jared.uitest;

import android.os.Bundle;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ListView msgListView;
    private EditText inputText;
    private Button send;
    private MsgAdapter adapter;

    private List<Msg> msgList = new ArrayList<Msg>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ActionBar actionBar = getSupportActionBar();
        actionBar.hide();

        setContentView(R.layout.activity_main);

        initMsgs();
        adapter = new MsgAdapter(MainActivity.this, R.layout.msg_item, msgList);
        inputText = (EditText)findViewById(R.id.input_text);
        send = (Button)findViewById(R.id.send);
        msgListView = (ListView)findViewById(R.id.msg_list_view);
        msgListView.setAdapter(adapter);
        send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String content = inputText.getText().toString();
                if(!"".equals(content)) {
                    Msg msg = new Msg(content, Msg.TYPE_SEND);
                    msgList.add(msg);
                    adapter.notifyDataSetChanged();
                    msgListView.setSelection(msgList.size());
                    inputText.setText("");
                }
            }
        });
    }

    private void initMsgs() {
        Msg msg1 = new Msg("Hello, how are you?", Msg.TYPE_RECEIVED);
        msgList.add(msg1);
        Msg msg2 = new Msg("Fine, thank you, and you?", Msg.TYPE_SEND);
        msgList.add(msg2);
        Msg msg3 = new Msg("I am fine, too!", Msg.TYPE_RECEIVED);
        msgList.add(msg3);
    }
}

    运行看下效果，输入一些文字，然后发送：

    上面这个界面已经和微信的也有点类似了，那么下面再加上个头像，那么会不会更好呢？我们来试试。首先准备两张头像的图片，简单命名为head1，head2，这里的头像最好喝聊天背景的height像素相同，本例子是45。然后修改msg_item.xml文件，代码如下：

<?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"
    android:padding="10dp">

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <ImageView
            android:id="@+id/head_left"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="left"
            android:src="@drawable/head1"/>

        <LinearLayout
            android:id="@+id/left_layout"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:layout_gravity="left"
            android:background="@drawable/left_messages">

            <TextView
                android:id="@+id/left_msg"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:layout_margin="10dp"
                android:textColor="#fff"/>
        </LinearLayout>
    </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:orientation="horizontal">

    <LinearLayout
        android:id="@+id/right_layout"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_gravity="right"
        android:background="@drawable/right_messages">

        <TextView
            android:id="@+id/right_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="10dp"/>

    </LinearLayout>
        <ImageView
            android:id="@+id/head_right"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/head2"/>
    </LinearLayout>

</LinearLayout>

    这里主要是头像的ImageView和聊天记录的TextView需要在同一行，所以这里LinearLayout里面又一次嵌套了LinearLayout。

    然后修改MsgAdapter代码如下：

package com.example.jared.uitest;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.util.List;

/**
 * Created by jared on 16/2/10.
 */
public class MsgAdapter extends ArrayAdapter<Msg> {
    private int resourceId;

    public MsgAdapter(Context context, int textViewResourceId, List<Msg> objects) {
        super(context, textViewResourceId, objects);
        resourceId = textViewResourceId;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
        Msg msg = getItem(position);
        View view;
        ViewHolder viewHolder;
        if(convertView == null) {
            view = LayoutInflater.from(getContext()).inflate(resourceId, null);
            viewHolder = new ViewHolder();
            viewHolder.leftLayout = (LinearLayout)view.findViewById(R.id.left_layout);
            viewHolder.rightLayout = (LinearLayout)view.findViewById(R.id.right_layout);
            viewHolder.leftMsg = (TextView)view.findViewById(R.id.left_msg);
            viewHolder.rightMsg = (TextView)view.findViewById(R.id.right_msg);
            viewHolder.head1 = (ImageView)view.findViewById(R.id.head_left);
            viewHolder.head2 = (ImageView)view.findViewById(R.id.head_right);
            view.setTag(viewHolder);
        } else {
            view = convertView;
            viewHolder = (ViewHolder) view.getTag();
        }
        if(msg.getType() == Msg.TYPE_RECEIVED) {
            viewHolder.leftLayout.setVisibility(View.VISIBLE);
            viewHolder.head1.setVisibility(View.VISIBLE);
            viewHolder.rightLayout.setVisibility(View.GONE);
            viewHolder.head2.setVisibility(View.GONE);
            viewHolder.leftMsg.setText(msg.getContent());
        } else if(msg.getType() == Msg.TYPE_SEND) {
            viewHolder.rightLayout.setVisibility(View.VISIBLE);
            viewHolder.head2.setVisibility(View.VISIBLE);
            viewHolder.leftLayout.setVisibility(View.GONE);
            viewHolder.head1.setVisibility(View.GONE);
            viewHolder.rightMsg.setText(msg.getContent());
        }
        return view;
    }

    class ViewHolder {
        LinearLayout leftLayout;
        LinearLayout rightLayout;
        TextView leftMsg;
        TextView rightMsg;
        ImageView head1;
        ImageView head2;
    }
}

    这里viewHolder中添加了head1和head2，然后获取资源中也添加了，并且添加了显示和隐藏的代码。

    图片，代码都准备好了，那就运行看看效果了：

    基本上和微信的聊天界面也有几分相似了。学习了这么多ui的知识，总算可以简单地开发一个界面了。ui就先学到这里，接下去继续学习别的知识吧。

附：源代码下载：https://github.com/imchenjianneng/emChatStudy

附：参考《第一行代码》