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Recommended implementation of combining characters implementation. (f…
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87
shell/platform/android/io/flutter/embedding/engine/android/AndroidKeyProcessor.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| package io.flutter.embedding.engine.android; | ||
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| import android.support.annotation.NonNull; | ||
| import android.support.annotation.Nullable; | ||
| import android.view.KeyCharacterMap; | ||
| import android.view.KeyEvent; | ||
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| import io.flutter.embedding.engine.systemchannels.KeyEventChannel; | ||
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| public class AndroidKeyProcessor { | ||
| private final KeyEventChannel keyEventChannel; | ||
| private int combiningCharacter; | ||
|
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| public AndroidKeyProcessor(@NonNull KeyEventChannel keyEventChannel) { | ||
| this.keyEventChannel = keyEventChannel; | ||
| } | ||
|
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| public void onKeyUp(@NonNull KeyEvent keyEvent) { | ||
| Character complexCharacter = applyCombiningCharacterToBaseCharacter(keyEvent.getUnicodeChar()); | ||
| keyEventChannel.keyUp( | ||
| new KeyEventChannel.FlutterKeyEvent(keyEvent, complexCharacter) | ||
| ); | ||
| } | ||
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| public void onKeyDown(@NonNull KeyEvent keyEvent) { | ||
| Character complexCharacter = applyCombiningCharacterToBaseCharacter(keyEvent.getUnicodeChar()); | ||
| keyEventChannel.keyDown( | ||
| new KeyEventChannel.FlutterKeyEvent(keyEvent, complexCharacter) | ||
| ); | ||
| } | ||
|
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| /** | ||
| * Applies the given Unicode character in {@code newCharacterCodePoint} to a previously | ||
| * entered Unicode combining character and returns the combination of these characters | ||
| * if a combination exists. | ||
| * <p> | ||
| * This method mutates {@link #combiningCharacter} over time to combine characters. | ||
| * <p> | ||
| * One of the following things happens in this method: | ||
| * <ul> | ||
| * <li>If no previous {@link #combiningCharacter} exists and the {@code newCharacterCodePoint} | ||
| * is not a combining character, then {@code newCharacterCodePoint} is returned.</li> | ||
| * <li>If no previous {@link #combiningCharacter} exists and the {@code newCharacterCodePoint} | ||
| * is a combining character, then {@code newCharacterCodePoint} is saved as the | ||
| * {@link #combiningCharacter} and null is returned.</li> | ||
| * <li>If a previous {@link #combiningCharacter} exists and the {@code newCharacterCodePoint} | ||
| * is also a combining character, then the {@code newCharacterCodePoint} is combined with | ||
| * the existing {@link #combiningCharacter} and null is returned.</li> | ||
| * <li>If a previous {@link #combiningCharacter} exists and the {@code newCharacterCodePoint} | ||
| * is not a combining character, then the {@link #combiningCharacter} is applied to the | ||
| * regular {@code newCharacterCodePoint} and the resulting complex character is returned. The | ||
| * {@link #combiningCharacter} is cleared.</li> | ||
| * </ul> | ||
| * <p> | ||
| * The following reference explains the concept of a "combining character": | ||
| * https://en.wikipedia.org/wiki/Combining_character | ||
| */ | ||
| @Nullable | ||
| private Character applyCombiningCharacterToBaseCharacter(int newCharacterCodePoint) { | ||
| if (newCharacterCodePoint == 0) { | ||
| return null; | ||
| } | ||
|
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| Character complexCharacter = (char) newCharacterCodePoint; | ||
| boolean isNewCodePointACombiningCharacter = (newCharacterCodePoint & KeyCharacterMap.COMBINING_ACCENT) != 0; | ||
| if (isNewCodePointACombiningCharacter) { | ||
| // If a combining character was entered before, combine this one with that one. | ||
| int plainCodePoint = newCharacterCodePoint & KeyCharacterMap.COMBINING_ACCENT_MASK; | ||
| if (combiningCharacter != 0) { | ||
| combiningCharacter = KeyCharacterMap.getDeadChar(combiningCharacter, plainCodePoint); | ||
| } else { | ||
| combiningCharacter = plainCodePoint; | ||
| } | ||
| } else { | ||
| // The new character is a regular character. Apply combiningCharacter to it, if it exists. | ||
| if (combiningCharacter != 0) { | ||
| int combinedChar = KeyCharacterMap.getDeadChar(combiningCharacter, newCharacterCodePoint); | ||
| if (combinedChar > 0) { | ||
| complexCharacter = (char) combinedChar; | ||
| } | ||
| combiningCharacter = 0; | ||
| } | ||
| } | ||
|
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| return complexCharacter; | ||
| } | ||
| } |
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