{"id":15,"date":"2009-01-18T17:06:50","date_gmt":"2009-01-19T00:06:50","guid":{"rendered":"http:\/\/www.connorgarvey.com\/blog\/?p=15"},"modified":"2010-02-12T09:45:54","modified_gmt":"2010-02-12T16:45:54","slug":"creating-soft-keys-that-work-with-text-watchers-in-android","status":"publish","type":"post","link":"https:\/\/connorgarvey.com\/blog\/?p=15","title":{"rendered":"Creating soft-keys that work with text watchers in Android"},"content":{"rendered":"

Recently, I created a screen with soft keys that could be used for number input.\u00a0 Scroll down for some source.<\/strong> Everything was working perfectly.\u00a0 Each number key called field.append(“1”), passing in the correct number.\u00a0 Then, a text watcher would be notified of the change and reformat the field.\u00a0 The problem arose when I wrote the backspace method.\u00a0 TextView doesn’t have a convenience method for removing characters from a field, so I used setText, passing in the number with the last character removed.\u00a0 Unfortunately, when I did that, the text wacher wasn’t notified of the change!\u00a0 Ugh…\u00a0 Android is very well designed, but some implementation details are really not written well.\u00a0 I decided it was time to look in the Android source.\u00a0 If the append method caused a notification to the text watcher, I would write a method that worked the same way.<\/p>\n

Supporting number keys<\/span><\/h2>\n

This was really simple.<\/p>\n

<\/a>Code block<\/a><\/td><\/a> <\/a> <\/a> <\/td><\/tr><\/table><\/div>
private<\/span> class<\/span> CharacterButtonListener implements<\/span>\n      View<\/span><\/a>.OnClickListener<\/span> {<\/span>\n    private<\/span> TextView field;<\/span>\n    private<\/span> String<\/span><\/a> character;<\/span>\n \n    public<\/span> CharacterButtonListener(<\/span>TextView field,\n        String<\/span><\/a> character)<\/span> {<\/span>\n      this<\/span>.field<\/span> =<\/span> field;<\/span>\n      this<\/span>.character<\/span> =<\/span> character;<\/span>\n    }<\/span>\n \n    @Override\n    public<\/span> void<\/span> onClick(<\/span>View<\/span><\/a> v)<\/span> {<\/span>\n      this<\/span>.field<\/span>.append<\/span>(<\/span>this<\/span>.character<\/span>)<\/span>;<\/span>\n    }<\/span>\n  }<\/span><\/pre><\/div><\/div>\n
Supporting the backspace key<\/span><\/h2>\n
Since the setText method wasn’t notifying the TextWatcher, I looked into Android’s source to find this solution.\u00a0 It’s ugly, but it works.<\/p>\n
<\/a>Code block<\/a><\/td><\/a> <\/a> <\/a> <\/td><\/tr><\/table><\/div>
this<\/span>.buttonBack<\/span>.setOnClickListener<\/span>(<\/span>new<\/span> View<\/span><\/a>.OnClickListener<\/span>(<\/span>)<\/span> {<\/span>\n      @Override\n      public<\/span> void<\/span> onClick(<\/span>View<\/span><\/a> v)<\/span> {<\/span>\n        TextView number =<\/span> numberText;<\/span>\n        CharSequence text =<\/span> number.getText<\/span>(<\/span>)<\/span>;<\/span>\n        \/\/ This is annoyingly ugly, but is from the Android source<\/span>\n        if<\/span> (<\/span>!<\/span>(<\/span>text instanceof<\/span> Editable)<\/span>)<\/span> {<\/span>\n          number.setText<\/span>(<\/span>text, BufferType.EDITABLE<\/span>)<\/span>;<\/span>\n        }<\/span>\n        Editable editable =<\/span> (<\/span>Editable)<\/span>number.getText<\/span>(<\/span>)<\/span>;<\/span>\n        \/\/ Now that we have the editable, edit it.<\/span>\n        \/\/ This line is not from the Android source.<\/span>\n        if<\/span> (<\/span>text.length<\/span>(<\/span>)<\/span> ><\/span> 0)<\/span> {<\/span>\n          editable.delete<\/span>(<\/span>text.length<\/span>(<\/span>)<\/span> -<\/span> 1, text.length<\/span>(<\/span>)<\/span>)<\/span>;<\/span>\n        }<\/span>\n      }<\/span>\n    }<\/span>)<\/span>;<\/span><\/pre><\/div><\/div>\n
That’s it! \u00a0 I tried another solution, having each soft-key fire a key event in the field.\u00a0  It worked, but since the field is automatically formatted, it didn’t feel right.\u00a0  Also, Android doesn’t let the application set the position of the cursor (caret) in the text view, so if the user re-opened the number input dialog to edit the number, the cursor appeared at the left side of the field, which meant that the user had to re-position the cursor before pressing any keys, which was a pain.<\/p>\n","protected":false},"excerpt":{"rendered":"
Recently, I created a screen with soft keys that could be used for number input.\u00a0 Scroll down for some source. Everything was working perfectly.\u00a0 Each number key called field.append(“1”), passing in the correct number.\u00a0 Then, a text watcher would be notified of the change and reformat the field.\u00a0 The problem arose when I wrote the […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[57],"tags":[3,4,7],"class_list":["post-15","post","type-post","status-publish","format-standard","hentry","category-android","tag-android","tag-java","tag-redpoint"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p1ql2n-f","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/15","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=15"}],"version-history":[{"count":16,"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/15\/revisions"}],"predecessor-version":[{"id":26,"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/15\/revisions\/26"}],"wp:attachment":[{"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=15"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=15"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/connorgarvey.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=15"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}