Question

我在main.java中使用下面的代码，这是工作！

FrameLayout view = (FrameLayout) findViewById(R.id.frame);
TextView product = new TextView(this);
product.setText("Product");
view.addView(product);

但我想添加CustomView，它不起作用

FrameLayout view = (FrameLayout) findViewById(R.id.frame);
CustomView v = new CustomView(this); //can't create new object
v.setImageResource(R.mipmap.scale);
view.addView(v);

如何通过addView添加CustomView？感谢

CustomView类

public CustomView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public CustomView(Context context) {
    this(context, null);
}

public CustomView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    obtainStyledAttributes(attrs);
    init();
}

attrs.xml

<resources>
    <declare-styleable name="CustomView">
        <attr name="src" format="reference" />           
        <attr name="editable" format="boolean"/>         
        <attr name="frameColor" format="color" />         
        <attr name="frameWidth" format="dimension" />    
        <attr name="framePadding" format="dimension" />  
        <attr name="degree" format="float" />           
        <attr name="scale" format="float" />              
        <attr name="controlDrawable" format="reference"/>
        <attr name="controlLocation">                    
            <enum name="left_top" value="0" />
            <enum name="right_top" value="1" />
            <enum name="right_bottom" value="2" />
            <enum name="left_bottom" value="3" />
        </attr>
    </declare-styleable>
</resources>

错误日志：

03-20 23:26:11.278: E/AndroidRuntime(6706): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=2, result=0, data=null} to activity {com.smallmouth./com.smallmouth..PhotoEdit}: java.lang.NullPointerException

Answer 1

您正在扩展View类（或视图类的某个子级）吗？如果是，则需要调用super方法并将上下文传递给构造函数中的父级，而不是您正在执行的操作。当前版本将是这样的

public class CustomView extends View {

public CustomView(Context context) {
    super(context);
}

public CustomView(Context context, AttributeSet attrs) {
    super(context, attrs);
}

public CustomView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
}
}

顺便说一句，你只需要第一个构造函数

如何使用addView添加CustomView？

1 个答案: