eclipse：Android 工程中 Graphical Layout Use View.isInEditMode() in your custom views to skip code when shown in Eclipse 错误分析及解决方法

The graphics preview in the layout editor may not be accurate:
Typeface.createFromAsset() is not supported. (Ignore for this session)

The following classes could not be instantiated:
- com.ifeegoo.debug.customviews.CustomFontFangZhengXiHeiTextView (Open Class, Show Error Log)
See the Error Log (Window > Show View) for more details.
Tip: Use View.isInEditMode() in your custom views to skip code when shown in Eclipse

java.lang.RuntimeException: native typeface cannot be made
    at android.graphics.Typeface.<init>(Typeface.java:175)
    at android.graphics.Typeface.createFromAsset(Typeface.java:149)
    at com.ifeegoo.debug.customviews.CustomFontFangZhengXiHeiTextView.<init>(CustomFontFangZhengXiHeiTextView.java:28)
    at sun.reflect.GeneratedConstructorAccessor34.newInstance(    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:408)
    at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.instantiateClass(ProjectCallback.java:437)
    at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.loadView(ProjectCallback.java:189)
    at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:207)
    at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:135)
    at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:755)
    at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:727)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:492)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:373)

<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:orientation="vertical"
    tools:context="com.ifeegoo.debug.activities.MainActivity" >

    <com.ifeegoo.debug.customviews.CustomFontFangZhengXiHeiTextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:gravity="center"
        android:textSize="50dp"
        android:text="ifeegoo" />

</LinearLayout>

我们找到报错的代码：

/**
 * 
 * @author ifeegoo www.ifeegoo.com
 *
 */
public class CustomFontFangZhengXiHeiTextView extends TextView
{
	public CustomFontFangZhengXiHeiTextView(Context context)
	{
		super(context);
	}

	public CustomFontFangZhengXiHeiTextView(Context context,
			AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);

		this.setTypeface(Typeface.createFromAsset(context.getAssets(),
				"font/fang_zheng_xi_hei.ttf"));
	}

	public CustomFontFangZhengXiHeiTextView(Context context, AttributeSet attrs)
	{
		super(context, attrs);

		this.setTypeface(Typeface.createFromAsset(context.getAssets(),
				"font/Cuisine.ttf"));
	}
}

我们再来看看提示的这个 View.isInEditMode() 这个方法：

    /**
     * Indicates whether this View is currently in edit mode. A View is usually
     * in edit mode when displayed within a developer tool. For instance, if
     * this View is being drawn by a visual user interface builder, this method
     * should return true.
     *
     * Subclasses should check the return value of this method to provide
     * different behaviors if their normal behavior might interfere with the
     * host environment. For instance: the class spawns a thread in its
     * constructor, the drawing code relies on device-specific features, etc.
     *
     * This method is usually checked in the drawing code of custom widgets.
     *
     * @return True if this View is in edit mode, false otherwise.
     */
    public boolean isInEditMode()
    {
        return false;
    }

以上方法的说明如下：

1.表示当前 View 是否处于编辑模式。一般来说，在开发者工具中显示时，这个 View 就是处于编辑模式。例如，如果这个 View 是通过可视的用户接口生成器绘制的话，这个方法应当返回 true。
2.如果说 View 的一般状态可能受到宿主环境的干扰，那么子类就应当校验这个方法的返回值以提供不同的状态。例如，在子类的构造器中创建一个线程， 或者绘制代码依赖于设备指定特性等。
3.通常这个方法在自定义控件绘制代码中被校验。
4.return True 如果当前 View 处于编辑模式, false 当前 View 处于非编辑模式。

/**
 * 
 * @author ifeegoo www.ifeegoo.com
 *
 */
public class CustomFontFangZhengXiHeiTextView extends TextView
{
	public CustomFontFangZhengXiHeiTextView(Context context)
	{
		super(context);
	}

	public CustomFontFangZhengXiHeiTextView(Context context,
			AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);

		if (!this.isInEditMode())
		{
			this.setTypeface(Typeface.createFromAsset(context.getAssets(),
					"font/fang_zheng_xi_hei.ttf"));
		}
	}

	public CustomFontFangZhengXiHeiTextView(Context context, AttributeSet attrs)
	{
		super(context, attrs);

		if (!this.isInEditMode())
		{
			this.setTypeface(Typeface.createFromAsset(context.getAssets(),
					"font/Cuisine.ttf"));
		}

	}
}

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