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Documentation Index

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The Tiempo tab (tab index 2) hosts TimeGraphView, a fully custom android.view.View that renders a live time-series graph using Android’s Canvas API. Every time a Wi-Fi scan completes, the graph appends a new data point for each detected network and redraws itself, giving you a continuous picture of how signal strength fluctuates over time. This view is especially useful for diagnosing intermittent drops, identifying roaming events, and comparing the relative stability of nearby access points.

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Axes and Grid

The graph occupies the full view with fixed padding on all four sides. Y-axis (signal strength)
  • Range: −100 dBm (bottom) to −20 dBm (top).
  • Grid lines are drawn every 10 dBm as dashed horizontal lines (DashPathEffect[10, 10]).
  • Each grid line is labelled in dBm on the left margin.
X-axis (scan index)
  • Represents the scan count index — a monotonically increasing integer label per scan cycle.
  • Dashed vertical grid lines align with each scan point.
  • Displays a sliding window of the last 10 scans from the stored history, so the graph never becomes cluttered regardless of how many total scans have been collected.
  • The x-axis title reads “Scan Count”.

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History Storage and Windowing

// In MainActivity.handleScanResults()
scanHistory.add(historyItem);
if (scanHistory.size() > 20) {
    scanHistory.remove(0);
}
  • Up to 20 scan cycles are retained in scanHistory.
  • TimeGraphView.updateHistory() receives the full list and internally slices the last 10 entries as the visible window.
  • When the history contains fewer than 10 cycles, the x-axis still reserves space for 10 points to keep the scale stable.

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Per-Network Line Rendering

Each unique BSSID gets its own colored line. Colors are assigned in rotation from a palette of seven:
IndexColorHex
0Cyan#00E5FF
1Green#00E676
2Yellow#FFC107
3Purple#D500F9
4Red#FF5252
5Orange#FF9100
6Blue#448AFF
Colors wrap around via index % colors.length for environments with more than seven networks.

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Signal-Based Line Style

Line opacity and stroke width vary based on the most recent RSSI reading for each network:
RSSI RangeAlphaStroke WidthInterpretation
< −80 dBm70 / 255 (~27 %)2.5 pxWeak signal
−80 to −60 dBm150 / 255 (~59 %)3.5 pxMedium signal
≥ −60 dBm255 / 255 (full)5.0 pxStrong signal
This means strong, nearby networks stand out with bold, fully-opaque lines while distant or marginal networks fade into the background. 
if (lastRssi < -80) {
    linePaint.setColor(Color.argb(70,  r, g, b)); // Weak
    linePaint.setStrokeWidth(2.5f);
} else if (lastRssi < -60) {
    linePaint.setColor(Color.argb(150, r, g, b)); // Medium
    linePaint.setStrokeWidth(3.5f);
} else {
    linePaint.setColor(color);                     // Strong — full opacity
    linePaint.setStrokeWidth(5.0f);
}
Lines are drawn with CornerPathEffect(25) for rounded corners, giving them a smooth, organic appearance rather than sharp angular turns.

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Legend Overlay

A semi-transparent dark box (#CC2E2E2E) is rendered in the upper-left corner of the graph area. It shows up to 6 network labels — each with a colored swatch matching its line color. Labels are truncated to 22 characters to fit within the fixed 320 px box width. Networks beyond the first 6 are drawn on the graph but omitted from the legend.

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Organic RSSI Jitter

If a network reports exactly the same RSSI as it did in the previous scan cycle, the app applies a small random variation: 
int sign = (Math.random() > 0.5) ? 1 : -1;
int variation = (int)(Math.random() * 2) + 1; // 1 or 2 dBm
level = result.level + (sign * variation);
This ±1–2 dBm jitter prevents perfectly flat horizontal lines in the graph — a visual artefact that can obscure real variation and make the chart look frozen. It is applied only when the incoming RSSI value is identical to the stored value for that BSSID.

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Auto-Scan Behavior

When the Tiempo tab is the active tab (currentTab == 2), the background autoUpdateTask Runnable fires every 5,000 ms and calls initiateWifiScan() directly. This bypasses the 30-second cooldown used by the manual scan button, ensuring a continuous stream of data points while the graph is visible. 
private final Runnable autoUpdateTask = new Runnable() {
    @Override
    public void run() {
        if (currentTab == 2) {
            initiateWifiScan();  // Fires every 5 s while Time Graph tab is active
        }
        autoUpdateHandler.postDelayed(this, 5000L);
    }
};
Switching away from the Tiempo tab does not cancel the handler tick — it simply skips the initiateWifiScan() call — so no unnecessary scans are triggered from other tabs.
The graph updates live only while the Time Graph tab is active. Switching to another tab suspends auto-scanning. When you return to the Tiempo tab, timeGraph.updateHistory(scanHistory) is called immediately in selectTab() to re-render the graph with whatever data has been accumulated, and auto-scanning resumes on the next 5-second tick.

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