android – NullPointerException在TextView.checkForRelayout(),而setText()

我试图实现ViewHolder模式,以便在绘图上绘制地图时提高性能.
我需要为我的标记创建一些标签.在draw()中的数据处理中调用此方法

// Now we create label view and convert it into bitmap
private Bitmap createLabelBitmap(GisLaborHistoryObject object,HistoryPoint point) {
    // create view from xml
    if (vh == null) {
        vh = new ViewHolder();
        vh.view = inflater.inflate(R.layout.map_gis_history_label,null,false);
        vh.tv = (TextView) vh.view.findViewById(R.id.gislabeltext);
    }

    // set label content
    if (vh.tv != null) {
        if (!mSingleLaborHistory) {
            String name = "";
            name = object.getdisplayName();
            if (name == null || "".equals(name))
                name = object.getPersonId();
            if (name == null || "".equals(name))
                name = object.getLaborCode();
            if (name == null)
                name = "";

            vh.tv.setText(name);
        } else
            vh.tv.setText(point.getChangeDate());
    } 
    // measure resulting view
    vh.view.measure(spec,spec);
    vh.view.layout(0,vh.view.getMeasuredWidth(),vh.view.getMeasuredHeight());
    Bitmap b = Bitmap.createBitmap(vh.view.getWidth(),vh.view.getHeight(),Bitmap.Config.ARGB_8888);
    canvasToDraw.setBitmap(b);
    canvasToDraw.translate(-vh.view.getScrollX(),-vh.view.getScrollY());
    vh.view.draw(canvasToDraw);
    return b;
}

规格是

spec = MeasureSpec.makeMeasureSpec(0,MeasureSpec.UNSPECIFIED);

结果是
logcat的：

04-29 17:12:34.057: E/AndroidRuntime(389): java.lang.NullPointerException
 04-29 17:12:34.057: E/AndroidRuntime(389):     at android.widget.TextView.checkForRelayout(TextView.java:5497)
 04-29 17:12:34.057: E/AndroidRuntime(389):     at android.widget.TextView.setText(TextView.java:2730)
 04-29 17:12:34.057: E/AndroidRuntime(389):     at android.widget.TextView.setText(TextView.java:2598)
 04-29 17:12:34.057: E/AndroidRuntime(389):     at android.widget.TextView.setText(TextView.java:2573)
 04-29 17:12:34.057: E/AndroidRuntime(389):     at com.xxx.android.proj.ui.map.overlays.LaborsMarkerOverlay.createLabelBitmap(LaborsMarkerOverlay.java:164)

我使用的XML布局

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/gislabeltext"
style="@style/labelStyle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingLeft="2dp"
android:paddingRight="2dp" />

可能是这个错误的原因？

解决方法

在看到android source code在5497行我注意到有一个检查使用mLayoutParams.我在调试模式下看起来就是这样,真的是空的！
我添加明确设置此参数的行.现在一切正常

vh.tv = (TextView) vh.view.findViewById(R.id.gislabeltext);
vh.tv.setLayoutParams(new ViewGroup.LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT));

我的错误是,当使用ViewGroup膨胀时,我必须显式设置LayoutParams root = null;一切正常,直到我尝试重用TextView乘法时间.