Android开发之WebView输入框提示解决办法

做基于WebView应用时，页面上有一个输入框，当输入的文字过多时，超过输入框的行数时，输入框能够滚动，这时间问题来了，输入的提示箭头会移动到输入框外，如何解决这个问题呢，查找chromium源码如下：

void LoadIfNecessary(jobject context) {
if (loaded_)
return;
loaded_ = true;
TRACE_EVENT0("browser", "HandleResources::Create");
JNIEnv* env = base::Android::AttachCurrentThread();
if (!context)
context = base::android::GetApplicationContext();
left_bitmap_ = CreateSkBitmapFromJavaBitmap(
Java_HandleViewResources_getLeftHandleBitmap(env, context));
right_bitmap_ = CreateSkBitmapFromJavaBitmap(
Java_HandleViewResources_getRightHandleBitmap(env, context));
center_bitmap_ = CreateSkBitmapFromJavaBitmap(
Java_HandleViewResources_getCenterHandleBitmap(env, context));
left_bitmap_.setImmutable();
right_bitmap_.setImmutable();
center_bitmap_.setImmutable();
drawable_horizontal_padding_ratio_ =
Java_HandleViewResources_getHandleHorizontalPaddingRatio(env);
}

这个函数加载这几个图片，在java端，

private static Bitmap getHandleBitmap(Context context, final int[] attrs) {
// TODO(jdduke): Properly derive and apply theme color.
TypedArray a = context.getTheme().obtainStyledAttributes(attrs);
final int resId = a.getResourceId(a.getIndex(0), 0);
final Resources res = a.getResources();
a.recycle();
final Bitmap.Config config = Bitmap.Config.ARGB_8888;
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = false;
options.inPreferredConfig = config;
Bitmap bitmap = BitmapFactory.decodeResource(res, resId, options);
savePic( bitmap);
if (bitmap != null) return bitmap;
// If themed resource lookup fails, fall back to using the Context's
// resources for attribute lookup.
if (res != context.getResources()) {
bitmap = BitmapFactory.decodeResource(context.getResources(), resId, options);
if (bitmap != null) return bitmap;
}
Drawable drawable = getHandleDrawable(context, attrs);
assert drawable != null;
final int width = drawable.getIntrinsicWidth();
final int height = drawable.getIntrinsicHeight();
Bitmap canvasBitmap = Bitmap.createBitmap(width, height, config);
Canvas canvas = new Canvas(canvasBitmap);
drawable.setBounds(0, 0, width, height);
drawable.draw(canvas);
return canvasBitmap;
}

C++中会调用java中的函数getHandleBitmap，这个函数通过 context.getTheme().obtainStyledAttributes 这个函数，从jdk中加载图片资源，显示时，通过GetBitmap函数获取到图像信息，通过layer_->SetBitmap( bitmap)设置显示的内容，函数如下：

const SkBitmap& GetBitmap(ui::TouchHandleOrientation orientation) {
DCHECK(loaded_);
switch (orientation) {
case ui::TouchHandleOrientation::LEFT:
return left_bitmap_;
case ui::TouchHandleOrientation::RIGHT:
return right_bitmap_;
case ui::TouchHandleOrientation::CENTER:
return center_bitmap_;
case ui::TouchHandleOrientation::UNDEFINED:
NOTREACHED() << "Invalid touch handle orientation.";
};
return center_bitmap_;
}

这么分析下来，想从显示下手解决这个问题，似乎不太可能，那只有替换图片资源，而图像资源是在android.jar包中，还有其他办法吗？ 分析源码，

public static Drawable getLeftHandleDrawable(Context context) {
return getHandleDrawable(context, LEFT_HANDLE_ATTRS);
}
public static Drawable getCenterHandleDrawable(Context context) {
return getHandleDrawable(context, CENTER_HANDLE_ATTRS);
}
public static Drawable getRightHandleDrawable(Context context) {
return getHandleDrawable(context, RIGHT_HANDLE_ATTRS);
}

有这几个图像id 信息，是不是可以重载呢，于是添加自己的

<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="MyTheme">
<item name="android:textSelectHandleLeft">@drawable/ic_launcher</item>
<item name="android:textSelectHandle">@drawable/aa</item>
<item name="android:textSelectHandleRight">@drawable/ic_launcher</item>
</style>
</resources>

替换掉系统的资源，再添加android:theme="@style/MyTheme" 自己的主题风格，问题解决