WebView输入框提示

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

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