midletstate.java

用于移动设备上的java虚拟机源代码

     * Signals the <code>MIDlet</code> to terminate and enter the
     * <i>DESTROYED</i> state.
     * In the destroyed state the <code>MIDlet</code> must release
     * all resources and save any persistent state. This method may
     * be called from the <i>PAUSED</i> or
     * <i>ACTIVE</i> states. <p>
     * <code>MIDlet</code>s should
     * perform any operations required before being terminated, such as
     * releasing resources or saving preferences or
     * state. <p>
     *
     * <b>NOTE:</b> The <code>MIDlet</code> can request that it not enter
     * the <i>DESTROYED</i>
     * state by throwing an <code>MIDletStateChangeException</code>. This
     * is only a valid response if the <code>unconditional</code>
     * flag is set to <code>false</code>. If it is <code>true</code>
     * the <code>MIDlet</code> is assumed to be in the <i>DESTROYED</i>
     * state regardless of how this method terminates. If it is not an
     * unconditional request, the <code>MIDlet</code> can signify that it
     * wishes
     * to stay in its current state by throwing the 
     * <code>MIDletStateChangeException</code>.
     * This request may be honored and the <code>destroy()</code>
     * method called again at a later time.
     *
     * @param unconditional If true when this method is called,
     * the <code>MIDlet</code> must cleanup and release all resources.
     * If false the <code>MIDlet</code> may throw 
     * <CODE>MIDletStateChangeException</CODE>
     * to indicate it does not want to be destroyed at this time.
     *
     * @exception MIDletStateChangeException is thrown if the
     * <code>MIDlet</code> wishes to continue to execute 
     * (Not enter the <i>DESTROYED</i> state).
     * This exception is ignored if <code>unconditional</code>
     * is equal to <code>true</code>.
     */
    protected abstract void destroyApp(boolean unconditional)
	throws MIDletStateChangeException;


    /**
     *
     * Used by a <code>MIDlet</code> to notify the application management
     * software that it has entered into the
     * <i>DESTROYED</i> state.  The application management software will not
     * call the MIDlet's <code>destroyApp</code> method, and all resources
     * held by the <code>MIDlet</code> will be considered eligible for
     * reclamation.
     * The <code>MIDlet</code> must have performed the same operations
     * (clean up, releasing of resources etc.) it would have if the
     * <code>MIDlet.destroyApp()</code> had been called.
     *
     */
    public final void notifyDestroyed() {
	synchronized (mutex) {
	    state = DESTROYED;
	    mutex.notify();
	}
    }

    /**
     * Used by a <code>MIDlet</code> to notify the application management
     * software that it has entered into the <i>PAUSED</i> state.
     * Invoking this method will
     * have no effect if the <code>MIDlet</code> is destroyed,
     * or if it has not yet been started. <p>
     * It may be invoked by the <code>MIDlet</code> when it is in the
     * <i>ACTIVE</i> state. <p>
     *
     * If a <code>MIDlet</code> calls <code>notifyPaused()</code>, in the
     * future its <code>startApp()</code> method may be called make
     * it active again, or its <code>destroyApp()</code> method may be
     * called to request it to destroy itself.
     */
    public final void notifyPaused() {
        int oldState;

	synchronized (mutex) {
            oldState = state;

            // do not notify the scheduler, since there is nothing to do
            setStateWithoutNotify(PAUSED);
	}

        // do work outside of the mutex
        if (oldState == ACTIVE) {
            displayManager.deactivate(getMIDlet());
        }
    }

    /**
     * Provides a <code>MIDlet</code> with a mechanism to retrieve
     * <code>MIDletSuite</code> for this MIDlet.
     *
     * @return MIDletSuite for this MIDlet
     */
    public final MIDletSuite getMIDletSuite() {
	return scheduler.getMIDletSuite();
    }

    /**
     * Used by a <code>MIDlet</code> to notify the application management
     * software that it is
     * interested in entering the <i>ACTIVE</i> state. Calls to
     * this method can be used by the application management software to
     * determine which applications to move to the <i>ACTIVE</i> state.
     * <p>
     * When the application management software decides to activate this  
     * application it will call the <code>startApp</code> method.
     * <p> The application is generally in the <i>PAUSED</i> state when this is
     * called.  Even in the paused state the application may handle
     * asynchronous events such as timers or callbacks.
     */

    public final void resumeRequest() {
        setState(PAUSED_RESUME);
    }

    /**
     * Requests that the device handle (e.g. display or install)
     * the indicated URL.
     *
     * <p>If the platform has the appropriate capabilities and
     * resources available, it SHOULD bring the appropriate
     * application to the foreground and let the user interact with
     * the content, while keeping the MIDlet suite running in the
     * background. If the platform does not have appropriate
     * capabilities or resources available, it MAY wait to handle the
     * URL request until after the MIDlet suite exits. In this case,
     * when the requesting MIDlet suite exits, the platform MUST then
     * bring the appropriate application to the foreground to let the
     * user interact with the content.</p>
     *
     * <p>This is a non-blocking method. In addition, this method does
     * NOT queue multiple requests. On platforms where the MIDlet
     * suite must exit before the request is handled, the platform
     * MUST handle only the last request made. On platforms where the
     * MIDlet suite and the request can be handled concurrently, each
     * request that the MIDlet suite makes MUST be passed to the
     * platform software for handling in a timely fashion.</p>
     *
     * <p>If the URL specified refers to a MIDlet suite (either an
     * Application Descriptor or a JAR file), the request is
     * interpreted as a request to install the named package. In this
     * case, the platform's normal MIDlet suite installation process
     * SHOULD be used, and the user MUST be allowed to control the
     * process (including cancelling the download and/or
     * installation). If the MIDlet suite being installed is an
     * <em>update</em> of the currently running MIDlet suite, the
     * platform MUST first stop the currently running MIDlet suite
     * before performing the update. On some platforms, the currently
     * running MIDlet suite MAY need to be stopped before any
     * installations can occur.</p>
     *
     * <p>If the URL specified is of the form
     * <code>tel:&lt;number&gt;</code>, as specified in <a
     * href="http://rfc.net/rfc2806.html">RFC2806</a>, then the
     * platform MUST interpret this as a request to initiate a voice
     * call. The request MUST be passed to the &quot;phone&quot;
     * application to handle if one is present in the platform.</p>
     *
     * <p>Devices MAY choose to support additional URL schemes beyond
     * the requirements listed above.</p>
     *
     * <p>Many of the ways this method will be used could have a
     * financial impact to the user (e.g. transferring data through a
     * wireless network, or initiating a voice call). Therefore the
     * platform MUST ask the user to explicitly acknowlege each
     * request before the action is taken. Implementation freedoms are
     * possible so that a pleasant user experience is retained. For
     * example, some platforms may put up a dialog for each request
     * asking the user for permission, while other platforms may
     * launch the appropriate application and populate the URL or
     * phone number fields, but not take the action until the user
     * explicitly clicks the load or dial buttons.</p>
     *
     * @return true if the MIDlet suite MUST first exit before the
     * content can be fetched.
     *
     * @param URL The URL for the platform to load.
     *
     * @exception ConnectionNotFoundException if
     * the platform cannot handle the URL requested.
     *
     * @since MIDP 2.0
     */
    public native final boolean platformRequest(String URL);

    /**
     * Change the state and notify.
     * Check to make sure the new state makes sense.
     * Changes to the status are protected by the mutex.
     * Any change to the state notifies the mutex.
     *
     * @param newState new state of the MIDlet
     */
    void setState(int newState) {
	synchronized (mutex) {
            setStateWithoutNotify(newState);
            mutex.notify();
	}
    }

    /**
     * Get the status of the specified permission.
     * If no API on the device defines the specific permission 
     * requested then it must be reported as denied.
     * If the status of the permission is not known because it might
     * require a user interaction then it should be reported as unknown.
     *
     * @param permission to check if denied, allowed, or unknown.
     * @return 0 if the permission is denied; 1 if the permission is allowed;
     * 	-1 if the status is unknown
     */
    public int checkPermission(String permission) {
        return getMIDletSuite().checkPermission(permission);
    }        

    /**
     * Change the state without notifing the scheduler.
     * Check to make sure the new state makes sense.
     * <p>
     * To be called only by the scheduler or MIDletState while holding
     * the scheduler mutex.
     *
     * @param newState new state of the MIDlet
     */
    void setStateWithoutNotify(int newState) {
        switch (state) {
        case DESTROYED:
            // can't set any thing else
            return;
        
        case DESTROY_PENDING:
            if (newState != DESTROYED) {
                // can only set DESTROYED
                return;
            }
            
            break;

        case PAUSED:
            if (newState == PAUSE_PENDING) {
                // already paused by app
                return;
            }

            break;

        case ACTIVE:
            if (newState == PAUSED_RESUME || newState == ACTIVE_PENDING) {
                // already active
                return;
            }
        }

        state = newState;
    }

    /**
     * Get the state.
     *
     * @return current state of the MIDlet.
     */
    int getState() {
	synchronized (mutex) {
	    return state;
	}
    }
}