为视图设置左边距... NullPointerException 即将到来

Question

我的代码这是一个适配器，我想在列表视图中将我的布局动态对齐到左侧和右侧...并且空指针异常出现在 relativeParams.leftMargin=80;

Java：

public View getView(int position, View view, ViewGroup parent)
    {
        ViewHolder viewHolder;
        ChatItem chatItem = getItem(position);
        viewAligned = view;
        if(view == null)
        {
            LayoutInflater layoutInflater = (LayoutInflater)  
            context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = layoutInflater.inflate(R.layout.cell_messages_layout, null);
            viewHolder = new ViewHolder();
            viewHolder.message = (TextView) view.findViewById(R.id.fromZoneMessage1);
            viewHolder.rl = (RelativeLayout) view.findViewById(R.id.messageLayout);
            view.setTag(viewHolder);
        }
        else
        {
            viewHolder = (ViewHolder) view.getTag();
        }

        viewHolder.message.setText(chatItem.getSenderMessage());
        if (chatItem.getAllignment() == 0)
        {
//          viewHolder.message.setGravity(Gravity.LEFT);
            viewHolder.message.setBackgroundResource(R.drawable.sent_message);
//          view.setBackgroundResource(R.drawable.sent_message);
        }
        else {
//          viewHolder.rl.setBackgroundResource(R.drawable.recieved_message);
//          view.holder.rl.set
//          viewHolder.message.setGravity(Gravity.RIGHT);
            viewHolder.message.setBackgroundResource(R.drawable.recieved_message);

            RelativeLayout.LayoutParams relativeParams = (RelativeLayout.LayoutParams) viewHolder.rl.getLayoutParams();
            relativeParams.leftMargin=80;
            viewHolder.rl.setLayoutParams(relativeParams);
//          LayoutParams lp = (LayoutParams) view.getLayoutParams();
        }
        return view;
    }

我的布局是....

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/messageLayout" 
   >


    <TextView 
        android:id="@+id/fromZoneMessage1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#000000"
        android:textSize="20dp"
        android:textStyle="bold"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="5dp"
        android:layout_marginBottom="5dp"
        android:layout_marginRight="10dp"
        android:padding="5dp"
        android:text="Hey Jack"
        />

</RelativeLayout>

请有人帮我把左边距放在我的视图中......

Answer 1

我只是将视图类型转换为相对布局并设置其重力...对于设置参数，意味着边距我在主要相对布局内采用了另一个虚拟相对布局并进行了调整。

你可以看下面的代码和相对布局

public View getView(int position, View view, ViewGroup parent)
    {
        ViewHolder viewHolder;
        ChatItem chatItem = getItem(position);
        viewAligned = view;
        if(view == null)
        {
            LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = layoutInflater.inflate(R.layout.cell_messages_layout, null);
            viewHolder = new ViewHolder();
            viewHolder.message = (TextView) view.findViewById(R.id.fromZoneMessage1);
            viewHolder.rl = (RelativeLayout) view.findViewById(R.id.messageLayout);
            view.setTag(viewHolder);
        }
        else
        {
            viewHolder = (ViewHolder) view.getTag();
        }

        viewHolder.message.setText(chatItem.getSenderMessage());
        if (chatItem.getAllignment() == 0)
        {

            viewHolder.message.setGravity(Gravity.LEFT);
            viewHolder.message.setBackgroundResource(R.drawable.recieved_message);
            ((RelativeLayout)view).setGravity(Gravity.RIGHT);
            android.widget.RelativeLayout.LayoutParams params = new LayoutParams(android.widget.RelativeLayout.LayoutParams.WRAP_CONTENT, android.widget.RelativeLayout.LayoutParams.WRAP_CONTENT);
            params.leftMargin = 50;
            viewHolder.rl.setLayoutParams(params);

                    }
        else {
            viewHolder.message.setGravity(Gravity.LEFT);
            viewHolder.message.setBackgroundResource(R.drawable.sent_message);
            ((RelativeLayout)view).setGravity(Gravity.LEFT);
            android.widget.RelativeLayout.LayoutParams params = new LayoutParams(android.widget.RelativeLayout.LayoutParams.WRAP_CONTENT, android.widget.RelativeLayout.LayoutParams.WRAP_CONTENT);
            params.rightMargin = 50;
            viewHolder.rl.setLayoutParams(params);
        }

        return view;
    }

布局

<?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="wrap_content"
   >

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/messageLayout" 
       >


    <TextView 
        android:id="@+id/fromZoneMessage1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="#000000"
        android:textSize="20dp"
        android:textStyle="bold"
        android:layout_marginLeft="10dp"
        android:layout_marginTop="5dp"
        android:layout_marginBottom="5dp"
        android:layout_marginRight="10dp"
        android:padding="5dp"
        android:text="Hey Jack"/>

</RelativeLayout>
</RelativeLayout>

Answer 2

尝试使用 AbsListView.LayoutParams 而不是使用 RelativeLayout.LayoutParams，因为您的视图位于 ListView 中。