I'm assuming you're using XML layout.
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:text="@string/**yourtextstring**"
/>
You can also use gravity center_vertical
or center_horizontal
according to your need.
and as @stealthcopter commented
in java: .setGravity(Gravity.CENTER);
Note: This is an updated answer. Comments below refer to an old version which messed around with keycodes.
JavaScript
Try it yourself on JSFiddle.
You can filter the input values of a text <input>
with the following setInputFilter
function (supports Copy+Paste, Drag+Drop, keyboard shortcuts, context menu operations, non-typeable keys, the caret position, different keyboard layouts, and all browsers since IE 9):
// Restricts input for the given textbox to the given inputFilter function.
function setInputFilter(textbox, inputFilter) {
["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
textbox.addEventListener(event, function() {
if (inputFilter(this.value)) {
this.oldValue = this.value;
this.oldSelectionStart = this.selectionStart;
this.oldSelectionEnd = this.selectionEnd;
} else if (this.hasOwnProperty("oldValue")) {
this.value = this.oldValue;
this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
} else {
this.value = "";
}
});
});
}
You can now use the setInputFilter
function to install an input filter:
setInputFilter(document.getElementById("myTextBox"), function(value) {
return /^\d*\.?\d*$/.test(value); // Allow digits and '.' only, using a RegExp
});
See the JSFiddle demo for more input filter examples. Also note that you still must do server side validation!
TypeScript
Here is a TypeScript version of this.
function setInputFilter(textbox: Element, inputFilter: (value: string) => boolean): void {
["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
textbox.addEventListener(event, function(this: (HTMLInputElement | HTMLTextAreaElement) & {oldValue: string; oldSelectionStart: number | null, oldSelectionEnd: number | null}) {
if (inputFilter(this.value)) {
this.oldValue = this.value;
this.oldSelectionStart = this.selectionStart;
this.oldSelectionEnd = this.selectionEnd;
} else if (Object.prototype.hasOwnProperty.call(this, 'oldValue')) {
this.value = this.oldValue;
if (this.oldSelectionStart !== null &&
this.oldSelectionEnd !== null) {
this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
}
} else {
this.value = "";
}
});
});
}
jQuery
There is also a jQuery version of this. See this answer.
HTML 5
HTML 5 has a native solution with <input type="number">
(see the specification), but note that browser support varies:
- Most browsers will only validate the input when submitting the form, and not when typing.
- Most mobile browsers don't support the
step
, min
and max
attributes.
- Chrome (version 71.0.3578.98) still allows the user to enter the characters
e
and E
into the field. Also see this question.
- Firefox (version 64.0) and Edge (EdgeHTML version 17.17134) still allow the user to enter any text into the field.
Try it yourself on w3schools.com.
Best Answer
Just in case anybody finds this, there's a nicer alternative that's not documented (I tripped over it after searching for hours, and finally found it in the bug list for the Android SDK itself). You CAN include raw HTML in strings.xml, as long as you wrap it in
Edge Cases:
'
and"
can be represented as\'
and\"
, or'
and"
.<
and>
always need to be escaped as<
and>
if you literally want them to render as '<' and '>' in the text.&qqq;
renders as&qqq;
, but<1
renders as<1
.Example:
Then, in your code:
IMHO, this is several orders of magnitude nicer to work with :-)
August 2021 update: My original answer used Html.fromHtml(String), which was deprecated in API 24. The alternative fromHtml(String,int) form is suggested as its replacement.
FROM_HTML_MODE_LEGACY is likely to work... but one of the other flags might be a better choice for what you want to do.
On a final note, if you'd prefer to render Android Spanned text suitable for use in a TextView using Markdown syntax instead of HTML, there are now multiple thirdparty libraries to make it easy including https://noties.io/Markwon.