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探究Android中ListView复用导致布局错乱的解决方案

时间：2020-10-06 21:53:56 | 栏目：Android代码 | 点击：次

首先来说一下具体的需求是什么样的：

需求如图所示，这里面有ABCD四个选项的题目，当点击A选项，如果A是正确的答案，则变成对勾的图案，如果是错误答案，则变成错误的图案，这里当时在写的时候觉得很简单，只要是在点击的时候判断我点击的选项与正确答案是否一样，是一样就将图片换成正确的样式，如果不一样就换成错误的样式，于是我便写了下面的代码(只贴出了核心Adapter中的代码)

package com.fizzer.anbangproject_dahuo_test.Adapter; 
import android.annotation.TargetApi; 
import android.content.Context; 
import android.graphics.drawable.Drawable; 
import android.os.Build; 
import android.text.TextUtils; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.TextView; 
import com.fizzer.anbangproject_dahuo_test.Model.ConvertModel; 
import com.fizzer.anbangproject_dahuo_test.R; 
import java.util.List; 
/** 
* Created by Fizzer on 2016/10/8. 
* Email: doraemonmqq@sina.com 
*/ 
public class ConvertViewAdapter extends BaseAdapter { 
private List<ConvertModel> list; 
private Context mContext; 
public ConvertViewAdapter(Context context, List<ConvertModel> list) { 
mContext = context; 
this.list = list; 
} 
@Override 
public int getCount() { 
if (list == null) { 
return 0; 
} else { 
return list.size(); 
} 
} 
@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
ViewHolder mViewHolder; 
if (convertView == null) { 
convertView = View.inflate(mContext, R.layout.view_upgradepartnet_topic_layout, null); 
mViewHolder = new ViewHolder(); 
mViewHolder.tvTitle = (TextView) convertView.findViewById(R.id.tvTitle); 
mViewHolder.tvSelectA = (TextView) convertView.findViewById(R.id.tvSelectA); 
mViewHolder.tvSelectB = (TextView) convertView.findViewById(R.id.tvSelectB); 
mViewHolder.tvSelectC = (TextView) convertView.findViewById(R.id.tvSelectC); 
mViewHolder.tvSelectD = (TextView) convertView.findViewById(R.id.tvSelectD); 
convertView.setTag(mViewHolder); 
} else { 
mViewHolder = (ViewHolder) convertView.getTag(); 
} 
ConvertModel module = list.get(position); 
mViewHolder.tvTitle.setText("Q" + (position + 1) + ":" + module.title); 
mViewHolder.tvSelectA.setText(module.optionA); 
mViewHolder.tvSelectB.setText(module.optionB); 
mViewHolder.tvSelectC.setText(module.optionC); 
mViewHolder.tvSelectD.setText(module.optionD); 
initListener(mViewHolder, module.rightOption, position, module); 
return convertView; 
} 
@Override 
public Object getItem(int position) { 
return null; 
} 
@Override 
public long getItemId(int position) { 
return 0; 
} 
private void initListener(final ViewHolder mViewHolder, final String select, final int position, final ConvertModel module) { 
mViewHolder.tvSelectA.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
judgeSelect(mViewHolder, mViewHolder.tvSelectA, "A", select, position); 
} 
}); 
mViewHolder.tvSelectB.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
judgeSelect(mViewHolder, mViewHolder.tvSelectB, "B", select, position); 
} 
}); 
mViewHolder.tvSelectC.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
judgeSelect(mViewHolder, mViewHolder.tvSelectC, "C", select, position); 
} 
}); 
mViewHolder.tvSelectD.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
judgeSelect(mViewHolder, mViewHolder.tvSelectD, "D", select, position); 
} 
}); 
} 
private void clearSelectState(ViewHolder mViewHolder) { 
mViewHolder.tvSelectA.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_a), null, null, null); 
mViewHolder.tvSelectB.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_b), null, null, null); 
mViewHolder.tvSelectC.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_c), null, null, null); 
mViewHolder.tvSelectD.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_d), null, null, null); 
} 
private void judgeSelect(ViewHolder viewHolder, TextView text, String select, String rightSelect, int position) { 
//清楚之前的状态 
clearSelectState(viewHolder); 
if (select.equals(rightSelect)) { 
text.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_right), null, null, null); 
} else { 
text.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_error), null, null, null); 
} 
} 
@TargetApi(Build.VERSION_CODES.LOLLIPOP) 
private Drawable getDrawableResource(int res) { 
Drawable drawable = mContext.getDrawable(res); 
drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight()); 
return drawable; 
} 
class ViewHolder { 
TextView tvTitle; 
TextView tvSelectA; 
TextView tvSelectB; 
TextView tvSelectC; 
TextView tvSelectD; 
} 
}

写完这段代码信心满满，觉得没问题了，但是在手机上一运行，发现出问题了，效果如下：

是的，由于listview的布局复用机制，导致下面没有选择的条目也因为复用而选择了选项

其实解决的方法很简单，就是将这个选中的条目与该条目对应的model相关联起来，具体怎么做呢，下面来仔细的分析分析，

首先在创建model的时候添加一个默认的字段，这个字段就是你选择的选项，当然初始值是没有的，在getView中对布局进行初始化的时候，就去判断这个字段是否有值，并且值为多少，如果有值，就去判断值为正确还是为错误，为正确则替换成正确的图片，如果为错误，则替换成错误的图片，如果没有值，则显示原始的ABCD四种初始化图片，这样，问题就迎刃而解了

下面贴出完整的代码，其实就跟上面的代码是差不多的，只不过在对model中添加的那个字段进行了一些复制与判断

package com.fizzer.anbangproject_dahuo_test.Adapter; 
import android.annotation.TargetApi; 
import android.content.Context; 
import android.graphics.drawable.Drawable; 
import android.os.Build; 
import android.text.TextUtils; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.TextView; 
import com.fizzer.anbangproject_dahuo_test.Model.ConvertModel; 
import com.fizzer.anbangproject_dahuo_test.R; 
import java.util.List; 
/** 
* Created by Fizzer on 2016/10/8. 
* Email: doraemonmqq@sina.com 
*/ 
public class ConvertViewAdapter extends BaseAdapter { 
private List<ConvertModel> list; 
private Context mContext; 
public ConvertViewAdapter(Context context, List<ConvertModel> list) { 
mContext = context; 
this.list = list; 
} 
@Override 
public int getCount() { 
if (list == null) { 
return 0; 
} else { 
return list.size(); 
} 
} 
@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
ViewHolder mViewHolder; 
if (convertView == null) { 
convertView = View.inflate(mContext, R.layout.view_upgradepartnet_topic_layout, null); 
mViewHolder = new ViewHolder(); 
mViewHolder.tvTitle = (TextView) convertView.findViewById(R.id.tvTitle); 
mViewHolder.tvSelectA = (TextView) convertView.findViewById(R.id.tvSelectA); 
mViewHolder.tvSelectB = (TextView) convertView.findViewById(R.id.tvSelectB); 
mViewHolder.tvSelectC = (TextView) convertView.findViewById(R.id.tvSelectC); 
mViewHolder.tvSelectD = (TextView) convertView.findViewById(R.id.tvSelectD); 
convertView.setTag(mViewHolder); 
} else { 
mViewHolder = (ViewHolder) convertView.getTag(); 
} 
ConvertModel module = list.get(position); 
mViewHolder.tvTitle.setText("Q" + (position + 1) + ":" + module.title); 
mViewHolder.tvSelectA.setText(module.optionA); 
mViewHolder.tvSelectB.setText(module.optionB); 
mViewHolder.tvSelectC.setText(module.optionC); 
mViewHolder.tvSelectD.setText(module.optionD); 
initListener(mViewHolder, module.rightOption, position, module); 
<span style="color:#cc0000;">if (TextUtils.isEmpty(module.check)) { 
clearSelectState(mViewHolder); 
} else { 
judgeSelect(mViewHolder, getCheckTextView(mViewHolder, module.check), module.check, module.rightOption, position); 
}</span> 
return convertView; 
} 
@Override 
public Object getItem(int position) { 
return null; 
} 
@Override 
public long getItemId(int position) { 
return 0; 
} 
private void initListener(final ViewHolder mViewHolder, final String select, final int position, final ConvertModel module) { 
mViewHolder.tvSelectA.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
<span style="color:#cc0000;">module.check = "A";</span> 
judgeSelect(mViewHolder, mViewHolder.tvSelectA, "A", select, position); 
} 
}); 
mViewHolder.tvSelectB.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
<span style="color:#cc0000;">module.check = "B";</span> 
judgeSelect(mViewHolder, mViewHolder.tvSelectB, "B", select, position); 
} 
}); 
mViewHolder.tvSelectC.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
<span style="color:#cc0000;">module.check = "C"; 
</span> judgeSelect(mViewHolder, mViewHolder.tvSelectC, "C", select, position); 
} 
}); 
mViewHolder.tvSelectD.setOnClickListener(new View.OnClickListener() { 
@Override 
public void onClick(View v) { 
<span style="color:#cc0000;">module.check = "D";</span> 
judgeSelect(mViewHolder, mViewHolder.tvSelectD, "D", select, position); 
} 
}); 
} 
private void clearSelectState(ViewHolder mViewHolder) { 
mViewHolder.tvSelectA.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_a), null, null, null); 
mViewHolder.tvSelectB.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_b), null, null, null); 
mViewHolder.tvSelectC.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_c), null, null, null); 
mViewHolder.tvSelectD.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_d), null, null, null); 
} 
private void judgeSelect(ViewHolder viewHolder, TextView text, String select, String rightSelect, int position) { 
//清楚之前的状态 
clearSelectState(viewHolder); 
if (select.equals(rightSelect)) { 
text.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_right), null, null, null); 
} else { 
text.setCompoundDrawables(getDrawableResource(R.drawable.ic_select_error), null, null, null); 
} 
} 
@TargetApi(Build.VERSION_CODES.LOLLIPOP) 
private Drawable getDrawableResource(int res) { 
Drawable drawable = mContext.getDrawable(res); 
drawable.setBounds(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight()); 
return drawable; 
} 
<span style="color:#cc0000;">private TextView getCheckTextView(ViewHolder mViewHolder, String rightSelect) { 
if ("A".equals(rightSelect)) { 
return mViewHolder.tvSelectA; 
} else if ("B".equals(rightSelect)) { 
return mViewHolder.tvSelectB; 
} else if ("C".equals(rightSelect)) { 
return mViewHolder.tvSelectC; 
} else if ("D".equals(rightSelect)) { 
return mViewHolder.tvSelectD; 
} 
return null; 
}</span> 
class ViewHolder { 
TextView tvTitle; 
TextView tvSelectA; 
TextView tvSelectB; 
TextView tvSelectC; 
TextView tvSelectD; 
} 
}

其中标红的就是新添的代码，加上这些后，问题就解决了，来看一下解决后的代码运行情况：

总结：

最后来总结一下这个问题的解决思路吧：

首先就是需要在该填充器对应的实体类中添加一个选中的(check)字段，在进行getview操作中，去根据这个check字段来进行相应的操作，如过有值，则设置成对应的样式，如果没有值，则设置成没有值得样式，当然，在用户点击的时候，要及时的对该字段进行赋值，类似的，像Listview中有checkbox也可以采用同样的方法来进行解决。

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