不朽情缘五滴血

書名： Flash Development for Android Cookbook
作者名： Joseph Labrecque
本章字數： 430字
更新時間： 2021-04-02 19:15:20

Verifying specific gesture support for common interactions

When dealing with Android devices, touch and gestures are the main mechanisms with which the user interacts with the device. If we want to use some of the predefined gestures in Flash Player and AIR, we can do so in the following manner.

How to do it...

To discover which specific gestures are supported on a device, perform the following actions:

First, import the following classes into your project:

import flash.display.StageScaleMode;
import flash.display.StageAlign;
import flash.display.Stage;
import flash.display.Sprite;
import flash.text.TextField;
import flash.text.TextFormat;
import flash.ui.Multitouch;
import flash.ui.MultitouchInputMode;

Declare a TextField and TextFormat object to allow visible output upon the device:
```
private var traceField:TextField;
private var traceFormat:TextFormat;
```

We will now set up our TextField, apply a TextFormat, and add it to the DisplayList. Here, we create a method to perform all of these actions for us:

protected function setupTextField():void {
traceFormat = new TextFormat();
traceFormat.bold = true;
traceFormat.font = "_sans";
traceFormat.size = 44;
traceFormat.align = "center";
traceFormat.color = 0x333333;
traceField = new TextField();
traceField.defaultTextFormat = traceFormat;
traceField.selectable = false;
traceField.mouseEnabled = false;
traceField.width = stage.stageWidth;
traceField.height = stage.stageHeight;
addChild(traceField);
}

Set the specific input mode for the multitouch APIs to support gestures with the following command:
```
Multitouch.inputMode = MultitouchInputMode.GESTURE;
```
Invoking Multitouch.supportedGestures will return a Vector of String objects naming all the supported gestured exposed to Flash on the device:
```
var supportedGestures:Vector.<String> = Multitouch.supportedGestures;
```
We can then look for a specific gesture or set of gestures to listen for, or fall back to other interaction events if necessary.
```
for(var i:int=0; i < supportedGestures.length; ++i) {
trace(supportedGestures[i]);
}
```

We can perform all of these necessary functions within a single method:

protected function checkGestures():void {
Multitouch.inputMode = MultitouchInputMode.GESTURE;
if(Multitouch.supportedGestures){
var supportedGestures:Vector.<String> = Multitouch.supportedGestures;
for(var i:int=0; i <supportedGestures.length; ++i) {
traceField.appendText(supportedGestures[i] + "\n");
}
}else{
traceField.appendText("no gesture support!");
}
}

The result will appear similar to the following:

How it works...

Flash player and AIR do a marvelous job of distilling information to essential details for an Android developer. Knowing which particular gestures are supported on a device will allow us to tailor event interactions on our applications and provide fallback interactions when necessary.

There's more...

In our example class, we also provide a check to be sure there are at least some gestures supported through Multitouch.supportedGestures. Chances are, if the device does provide gesture support, we will want to provide a warning to the user explaining that the application will not perform optimally because of hardware limitations.

Apart from the more common gestures such as zoom, swipe, rotate, and pan, which are included in the flash.events.TransformGestureEvent package, there are additional, yet less common gestures such as two-finger tap, found in the flash.events.GestureEvent and flash.events.PressAndTapGestureEvent classes. These will all be referenced by Multitouch.supportedGestures if available on the device.

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Flash Development for Android Cookbook

Verifying specific gesture support for common interactions

How to do it...

How it works...

There's more...