ListView的優化及顯示

最近做一個有聊天界面的應用，從服務器獲取數據，顯示有問題，如下圖

這種錯誤真令人噁心，開始以爲是優化代碼搞出來的問題，仔細看了下，沒問題，估計是緩存的問題，

佈局代碼如下：

<?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" >

    <TableLayout
        android:id="@+id/tl_item_send"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:padding="3dp"
        android:shrinkColumns="0">

        <TableRow
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:gravity="right|top"
             >

            <TextView
                android:id="@+id/tv_item_send"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="50dp"
                android:background="@drawable/conversion_send"
                android:text="ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss疼啊蛋疼啊頭也疼啊"
                android:textColor="#000000"
                android:textSize="18sp" />

            <ImageView
                android:id="@+id/iv_item_send"
                android:layout_width="70dp"
                android:layout_height="70dp"
                android:layout_marginRight="10dp"
                android:background="@drawable/account" />

            <ImageView
                android:id="@+id/iv_sendAvatar"
                android:layout_width="45dp"
                android:layout_height="45dp"
                android:layout_marginRight="10dp"
                android:layout_marginTop="10dp"
                android:background="@drawable/circle_send" />
        </TableRow>
    </TableLayout>

    <TableLayout
        android:id="@+id/tl_item_receive"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:padding="3dp"
            android:visibility="gone"
        android:shrinkColumns="2">

        <TableRow
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:gravity="left|top" 
            >

            <ImageView
                android:id="@+id/iv_receiverAvatar"
                android:layout_width="45dp"
                android:layout_height="45dp"
                android:layout_marginRight="10dp"
                android:background="@drawable/circle_send" />

            <ImageView
                android:id="@+id/iv_item_receive"
                android:layout_width="70dp"
                android:layout_height="70dp"
                android:background="@drawable/account"/>

            <TextView
                android:id="@+id/tv_item_receiver"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginRight="50dp"
                android:background="@drawable/conversion_receiver"
                android:gravity="center_vertical"
                android:text="ssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss疼啊蛋疼啊頭也疼啊"
                android:textColor="#000000"
                android:textSize="18sp"/>
        </TableRow>
    </TableLayout>

</LinearLayout>

BaseAadapter中的getView代碼如下：

public View getView(int position, View convertView, ViewGroup parent) {
		View view;
		ViewHolder holder = null;
		if(convertView != null){
			view = convertView;
			holder = (ViewHolder) view.getTag();
		}else{
			view = View.inflate(context, R.layout.item_conversion_detail, null);
			holder = new ViewHolder();
			holder.tl_item_send = view.findViewById(R.id.tl_item_send);
			holder.tv_item_send = (TextView) view.findViewById(R.id.tv_item_send);
			holder.iv_sendAvatar = (ImageView) view.findViewById(R.id.iv_sendAvatar);
			holder.iv_item_send = (ImageView) view.findViewById(R.id.iv_item_send);
			
			holder.tl_item_receive = view.findViewById(R.id.tl_item_receive);
			holder.tv_item_receiver = (TextView) view.findViewById(R.id.tv_item_receiver);
			holder.iv_receiverAvatar = (ImageView) view.findViewById(R.id.iv_receiverAvatar);
			holder.iv_item_receive = (ImageView) view.findViewById(R.id.iv_item_receive);
			view.setTag(holder);
		}
		if(conservationList.get(position).getIsSend()){//若是發送的會話
			holder.tl_item_send.setVisibility(View.VISIBLE);
			if(conservationList.get(position).getIsTV()){//若會話內容是字符串
				holder.tv_item_send.setVisibility(View.VISIBLE);
				holder.iv_item_send.setVisibility(View.GONE);
				holder.tv_item_send.setText(position + ":"+ conservationList.get(position).getSendStr());
			}else{//若會話內容是圖片
				holder.tv_item_send.setVisibility(View.GONE);
				holder.iv_item_send.setVisibility(View.VISIBLE);
				holder.iv_item_send.setBackgroundResource(R.drawable.consult);
			}
//		}else{//若是接收到的會話
		}else if(!conservationList.get(position).getIsSend()){//若是接收到的會話
			holder.tl_item_receive.setVisibility(View.VISIBLE);
			if(conservationList.get(position).getIsTV()){//若會話內容是字符串
				holder.tv_item_receiver.setVisibility(View.VISIBLE);
				holder.iv_item_receive.setVisibility(View.GONE);
				holder.tv_item_receiver.setText(position + ":"+ conservationList.get(position).getReceiveStr());
			}else{//若會話內容是圖片
				holder.tv_item_receiver.setVisibility(View.GONE);
				holder.iv_item_receive.setVisibility(View.VISIBLE);
				holder.iv_item_receive.setBackgroundResource(R.drawable.consult);
			}
		}
		return view;
	}

其中ViewHolder是一個防止多次findViewById的類，以空間換時間的做法，代碼：

static class ViewHolder{
		public View tl_item_send;
		public TextView tv_item_send;
		public ImageView iv_sendAvatar;
		public ImageView iv_item_send;
		
		public View tl_item_receive;
		public TextView tv_item_receiver;
		public ImageView iv_receiverAvatar;
		public ImageView iv_item_receive;
		
	}

後來發現是省懶勁，以爲佈局中爲每個view設置了visibility=gone在代碼中就不必要再某些地方加代碼xxx.setVisibility(View.GONE);了，其實這一句是非常重要的，不然當在某一個地方讓這個view顯示後，緩存中就存有這個效果，然後會莫名其妙的在其他地方出現了這個效果，令人蛋疼。。。

將getView的代碼稍微加上幾句看似緊要的代碼即可正常：

	public View getView(int position, View convertView, ViewGroup parent) {
		View view;
		ViewHolder holder = null;
		if(convertView != null){
			view = convertView;
			holder = (ViewHolder) view.getTag();
		}else{
			view = View.inflate(context, R.layout.item_conversion_detail, null);
			holder = new ViewHolder();
			holder.tl_item_send = view.findViewById(R.id.tl_item_send);
			holder.tv_item_send = (TextView) view.findViewById(R.id.tv_item_send);
			holder.iv_sendAvatar = (ImageView) view.findViewById(R.id.iv_sendAvatar);
			holder.iv_item_send = (ImageView) view.findViewById(R.id.iv_item_send);
			
			holder.tl_item_receive = view.findViewById(R.id.tl_item_receive);
			holder.tv_item_receiver = (TextView) view.findViewById(R.id.tv_item_receiver);
			holder.iv_receiverAvatar = (ImageView) view.findViewById(R.id.iv_receiverAvatar);
			holder.iv_item_receive = (ImageView) view.findViewById(R.id.iv_item_receive);
			view.setTag(holder);
		}
		if(conservationList.get(position).getIsSend()){//若是發送的會話
			holder.tl_item_send.setVisibility(View.VISIBLE);
 			holder.tl_item_receive.setVisibility(View.GONE);
			if(conservationList.get(position).getIsTV()){//若會話內容是字符串
				holder.tv_item_send.setVisibility(View.VISIBLE);
				holder.iv_item_send.setVisibility(View.GONE);
				holder.tv_item_send.setText(position + ":"+ conservationList.get(position).getSendStr());
			}else{//若會話內容是圖片
				holder.tv_item_send.setVisibility(View.GONE);
				holder.iv_item_send.setVisibility(View.VISIBLE);
				holder.iv_item_send.setBackgroundResource(R.drawable.consult);
			}
//		}else{//若是接收到的會話
		}else if(!conservationList.get(position).getIsSend()){//若是接收到的會話
 			holder.tl_item_send.setVisibility(View.GONE);
			holder.tl_item_receive.setVisibility(View.VISIBLE);
			if(conservationList.get(position).getIsTV()){//若會話內容是字符串
				holder.tv_item_receiver.setVisibility(View.VISIBLE);
				holder.iv_item_receive.setVisibility(View.GONE);
				holder.tv_item_receiver.setText(position + ":"+ conservationList.get(position).getReceiveStr());
			}else{//若會話內容是圖片
				holder.tv_item_receiver.setVisibility(View.GONE);
				holder.iv_item_receive.setVisibility(View.VISIBLE);
				holder.iv_item_receive.setBackgroundResource(R.drawable.consult);
			}
		}
		return view;
	}

正常顯示：