Android開發之WebView輸入框提示解決辦法

做基於WebView應用時，頁面上有一個輸入框，當輸入的文字過多時，超過輸入框的行數時，輸入框能夠滾動，這時間問題來了，輸入的提示箭頭會移動到輸入框外，如何解決這個問題呢，查找chromium源碼如下：

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);
}

這個函數加載這幾個圖片，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++中會調用java中的函數getHandleBitmap，這個函數通過 context.getTheme().obtainStyledAttributes 這個函數，從jdk中加載圖片資源，顯示時，通過GetBitmap函數獲取到圖像信息，通過layer_->SetBitmap( bitmap)設置顯示的內容，函數如下：

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_;
}

這麼分析下來，想從顯示下手解決這個問題，似乎不太可能，那只有替換圖片資源，而圖像資源是在android.jar包中，還有其他辦法嗎？ 分析源碼，

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);
}

有這幾個圖像id 信息，是不是可以重載呢，於是添加自己的

<?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>

替換掉系統的資源，再添加android:theme="@style/MyTheme" 自己的主題風格，問題解決