android的一个UI的小问题，关于图片伸缩的

Question

 <?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_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="left"   
        android:background="@drawable/message_left" >

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

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

        <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>

 package com.example.chatapp;

import java.util.List;

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;

public class MsgAdapter extends ArrayAdapter<Msg> {

    private int resourceId;

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

    @Override
    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());
        }
        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;
    }
}

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#d8e0e8"
    android:orientation="vertical" >

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

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

        <EditText
            android:id="@+id/input_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="5"
            android:maxLines="2" />

        <Button
            android:id="@+id/sent_button"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:padding="3dp"
            android:text="发送" />
    </LinearLayout>

</LinearLayout>

package com.example.chatapp;

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

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

public class MainActivity extends Activity {

    private ListView msgListView;
    private EditText inputText;
    private Button sentButton;
    private MsgAdapter msgAdapter;
    private List<Msg> msgList = new ArrayList<Msg>();

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initMsgs();
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_main);
        msgAdapter = new MsgAdapter(MainActivity.this, R.layout.msg_item,
                msgList);
        msgListView = (ListView) findViewById(R.id.msg_list_view);
        msgListView.setAdapter(msgAdapter);
    }

    private void initMsgs() {
        Msg m1 = new Msg("Hello~", Msg.TYPE_RECEIVED);
        msgList.add(m1);
        Msg m2 = new Msg("Who are you?", Msg.TYPE_SEND);
        msgList.add(m2);
        Msg m3 = new Msg("I'm your father", Msg.TYPE_RECEIVED);
        msgList.add(m3);
    }

}

package com.example.chatapp;

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;
    }

}

为什么消息框不会伸缩

Answer 1

http://blog.csdn.net/android_jeck/article/details/8957777