getCompoundDrawables

方法简介：

用于获取当下该控件的上下左右位置的Drawable引用，该方法返回的是Drawable[]数组，length为4，分别对应Left，Top，Right和Bottom的Drawable引用。比如：以下代码的Edittext，drawable[2]就对应于EditText控件的右端。在代码中动态添加图标就用到这个方法，相当于XML文件中的drawableRight。

代码：

public class ClearableEditText extends EditText implements View.OnTouchListener,View.OnFocusChangeListener,TextWatcher {

    public interface Listener {
        void didClearText();
    }

    public void setListener(Listener listener) {
        this.listener = listener;
    }

    private Drawable xD;
    private Listener listener;

    public ClearableEditText(Context context) {
        super(context);
        init();
    }

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

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

    @Override
    public void setOnTouchListener(OnTouchListener l) {
        this.l = l;
    }

    @Override
    public void setOnFocusChangeListener(OnFocusChangeListener f) {
        this.f = f;
    }

    private OnTouchListener l;
    private OnFocusChangeListener f;

    @Override
    public boolean onTouch(View v,MotionEvent event) {
        if (getCompoundDrawables()[2] != null) {
            boolean tappedX = event.getX() > (getWidth() - getPaddingRight() - xD
                    .getIntrinsicWidth());
            if (tappedX) {
                if (event.getAction() == MotionEvent.ACTION_UP) {
                    setText("");
                    if (listener != null) {
                        listener.didClearText();
                    }
                }
                return true;
            }
        }
        if (l != null) {
            return l.onTouch(v,event);
        }
        return false;
    }

    @Override
    public void onFocusChange(View v,boolean hasFocus) {
        if (hasFocus) {
            setClearIconVisible(getText().length() > 0);
        } else {
            setClearIconVisible(false);
        }
        if (f != null) {
            f.onFocusChange(v,hasFocus);
        }
    }

    @Override
    public void onTextChanged(CharSequence s,int start,int before,int count) {
        if (isFocused()) {
            setClearIconVisible(getText().length() > 0);
        }
    }

    @Override
    public void beforeTextChanged(CharSequence s,int count,int after) {

    }

    @Override
    public void afterTextChanged(Editable s) {

    }

    private void init() {
        xD = getCompoundDrawables()[2];
        if (xD == null) {
            xD = getResources()
                    .getDrawable(android.R.drawable.presence_offline);
        }
        xD.setBounds(0,0,xD.getIntrinsicWidth(),xD.getIntrinsicHeight());
        setClearIconVisible(false);
        super.setOnTouchListener(this);
        super.setOnFocusChangeListener(this);
        addTextChangedListener(this);
    }

    protected void setClearIconVisible(boolean visible) {
        boolean wasVisible = (getCompoundDrawables()[2] != null);
        if (visible != wasVisible) {
            Drawable x = visible ? xD : null;
            setCompoundDrawables(getCompoundDrawables()[0],getCompoundDrawables()[1],x,getCompoundDrawables()[3]);
        }
    }

}

拓展：

登录界面经常用到密码的显示和隐藏按钮，实现如下代码：

loginPswEt.setTransformationMethod(HideReturnsTransformationMethod.getInstance());//隐藏密码
            loginPswEt.setTransformationMethod(PasswordTransformationMethod.getInstance());//显示密码

此至！