Android 自定义 view 连接输入法

在 View 的源码里面有一个方法名为： onCreateInputConnection , 通过该方法可使自定义 view 连接 inputMethod, 可以接受输入信息。该方法的解释如下：

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/**
 * Create a new InputConnection for an InputMethod to interact
 * with the view.  The default implementation returns null, since it doesn't
 * support input methods.  You can override this to implement such support.
 * This is only needed for views that take focus and text input.
 *
 * <p>When implementing this, you probably also want to implement
 * {@link #onCheckIsTextEditor()} to indicate you will return a
 * non-null InputConnection.</p>
 *
 * <p>Also, take good care to fill in the {@link android.view.inputmethod.EditorInfo}
 * object correctly and in its entirety, so that the connected IME can rely
 * on its values. For example, {@link android.view.inputmethod.EditorInfo#initialSelStart}
 * and  {@link android.view.inputmethod.EditorInfo#initialSelEnd} members
 * must be filled in with the correct cursor position for IMEs to work correctly
 * with your application.</p>
 *
 * @param outAttrs Fill in with attribute information about the connection.
 */
public InputConnection onCreateInputConnection(EditorInfo outAttrs) {
    return null;
}

onCreateInputConnection 方法连接了 view 和 inputMethod，通过创建一个 InputConnection 来接受输入法的信息。

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/**
 * Created by hanks on 2017/2/16.
 */

public class KInputConnection extends BaseInputConnection {

    public KInputConnection(View targetView, boolean fullEditor) {
        super(targetView, fullEditor);
    }

    // 输入法的按键信息
    @Override
    public boolean sendKeyEvent(KeyEvent event) {
        switch (event.getKeyCode()) {
            case KeyEvent.KEYCODE_DEL:
                if (event.getAction()== KeyEvent.ACTION_UP
                        && onCommitTextListener != null) {
                    onCommitTextListener.onDeleteText();
                }
                break;
        }
        return super.sendKeyEvent(event);
    }
    
    // 输入法提交了一个 text
    @Override
    public boolean commitText(CharSequence text, int newCursorPosition) {
        if (onCommitTextListener != null) {
            onCommitTextListener.commitText(text, newCursorPosition);
        }
        return true;
    }

    private OnCommitTextListener  onCommitTextListener;

    public void setOnCommitTextListener(OnCommitTextListener onCommitTextListener) {
        this.onCommitTextListener = onCommitTextListener;
    }

    public interface OnCommitTextListener {
        boolean commitText(CharSequence text, int newCursorPosition);

        void onDeleteText();
    }
}

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/**
 * 支持输入法的 view
 * Created by hanks on 2017/2/16.
 */

public class KInputView extends View {

    private StringBuilder content = new StringBuilder();
    private KInputConnection inputConnection;
    private TextPaint paint;
    private InputMethodManager inputMethodManager;

    public KInputView(Context context) {
        this(context, null);
    }

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

    private void init() {

        // 设置可以接受到焦点
        this.setFocusable(true);
        this.setFocusableInTouchMode(true);

        // 获取 InputMethodManager
        inputMethodManager = (InputMethodManager) getContext().getSystemService(Context.INPUT_METHOD_SERVICE);

        paint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(Color.BLUE);
        float textSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 14, getResources().getDisplayMetrics());
        paint.setTextSize(textSize);
        setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                // 弹出、关闭输入法
                inputMethodManager.toggleSoftInput(0, InputMethodManager.HIDE_NOT_ALWAYS);
            }
        });
    }

    @Override
    public InputConnection onCreateInputConnection(EditorInfo editorInfo) {
        return getInputConnection(editorInfo);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // 使用 StaticLayout 来 draw
        new StaticLayout(content, paint, getWidth(), Layout.Alignment.ALIGN_NORMAL, 1.5f, 0, false).draw(canvas);
    }

    private InputConnection getInputConnection(EditorInfo editorInfo) {
        if (inputConnection != null) {
            return inputConnection;
        }
        inputConnection = new KInputConnection(this, false);
        inputConnection.setOnCommitTextListener(new KInputConnection.OnCommitTextListener() {
            @Override
            public boolean commitText(CharSequence text, int newCursorPosition) {
                content.append(text);
                invalidate();
                return false;
            }

            @Override
            public void onDeleteText() {
                if (content.length() <= 0) {
                    return;
                }
                content.deleteCharAt(content.length() - 1);
                invalidate();
            }
        });
        return inputConnection;
    }
}

效果图

自定义 View