如何使用 isInEditMode()在编辑器中查看具有自定义视图的布局

我必须编辑一个具有自定义视图的软件，当我试图编辑布局 xml 时，Eclipse 告诉我:

在自定义视图中使用 View.isInEditMode ()可以在显示时跳过代码 在 Eclipse

但我不知道 怎么做和 哪里我必须在应用程序中使用 IsInEditMode ()

我的 xml 文件是

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ff000000"
>
<TextView
android:id="@+id/result"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="right"
android:textSize="32dip"
android:scrollbars="none"
android:lines="1"
android:freezesText="true"
android:textColor="@color/result"
/>
<EditText
android:id="@+id/input"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="left"
android:textSize="28dip"
android:scrollbars="none"
android:singleLine="true"
android:autoText="false"
android:imeOptions="flagNoEnterAction|flagNoExtractUi"
/>
<ListView
android:id="@+id/history"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:cacheColorHint="#ff000000"
android:choiceMode="singleChoice"
android:scrollbarStyle="outsideInset"
android:scrollbars="none"
/>
<calculator.GraphView
android:id="@+id/graph"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:visibility="gone"
/>
<include layout="@layout/keyboard" />
</LinearLayout>

我的 GraphView 是

public class GraphView extends View implements Grapher,
ZoomButtonsController.OnZoomListener,
TouchHandler.TouchHandlerInterface {
private int width, height;
private Matrix matrix = new Matrix();
private Paint paint = new Paint();
private Paint textPaint = new Paint();
private ArrayList<Function> funcs = new ArrayList<Function>();
private Data next = new Data(), endGraph = new Data();
private Data graphs[] = { new Data(), new Data(), new Data(), new Data(),
new Data() };
private static final int GRAPHS_SIZE = 5;
private float gwidth = 8;
private float currentX, currentY;
private float lastMinX;
private Scroller scroller;
private float boundMinY, boundMaxY;
protected ZoomButtonsController zoomController = new ZoomButtonsController(
this);
private ZoomTracker zoomTracker = new ZoomTracker();
private TouchHandler touchHandler;
private float lastTouchX, lastTouchY;


private static final int COL_AXIS = 0xff00a000, COL_GRID = 0xff004000,
COL_TEXT = 0xff00ff00;


private static final int COL_GRAPH[] = { 0xffffffff, 0xff00ffff,
0xffffff00, 0xffff00ff, 0xff80ff80 };


public GraphView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}


public GraphView(Context context) {
super(context);
touchHandler = new TouchHandler(this);
init(context);
}


private void init(Context context) {
zoomController.setOnZoomListener(this);
scroller = new Scroller(context);
paint.setAntiAlias(false);
textPaint.setAntiAlias(true);
}


@SuppressLint("WrongCall")
public String captureScreenshot() {
Bitmap bitmap = Bitmap.createBitmap(width, height,
Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
onDraw(canvas);
return Util.saveBitmap(bitmap, Grapher.SCREENSHOT_DIR, "calculator");
}


private void clearAllGraph() {
for (int i = 0; i < GRAPHS_SIZE; ++i) {
graphs[i].clear();
}
}


public void setFunctions(ArrayList<Function> fs) {
funcs.clear();
for (Function f : fs) {
int arity = f.arity();
if (arity == 0 || arity == 1) {
funcs.add(f);
}
}
clearAllGraph();
invalidate();
}


public void setFunction(Function f) {
funcs.clear();
if (f != null) {
funcs.add(f);
}
clearAllGraph();
invalidate();
}


public void onVisibilityChanged(boolean visible) {
}


public void onZoom(boolean zoomIn) {
if (zoomIn) {
if (canZoomIn()) {
gwidth /= 2;
invalidateGraphs();
}
} else {
if (canZoomOut()) {
gwidth *= 2;
invalidateGraphs();
}
}
zoomController.setZoomInEnabled(canZoomIn());
zoomController.setZoomOutEnabled(canZoomOut());
}


public void onResume() {
}


public void onPause() {
}


public void onDetachedFromWindow() {
zoomController.setVisible(false);
super.onDetachedFromWindow();
}


protected void onSizeChanged(int w, int h, int ow, int oh) {
width = w;
height = h;
clearAllGraph();
}


protected void onDraw(Canvas canvas) {
if (funcs.size() == 0) {
return;
}
if (scroller.computeScrollOffset()) {
final float scale = gwidth / width;
currentX = scroller.getCurrX() * scale;
currentY = scroller.getCurrY() * scale;
if (!scroller.isFinished()) {
invalidate();
}
}
drawGraph(canvas);
}


private float eval(Function f, float x) {
float v = (float) f.eval(x);


if (v < -10000f) {
return -10000f;
}
if (v > 10000f) {
return 10000f;
}
return v;
}


private float distance2(float x1, float y1, float x2, float y2, float y) {
final float dx = x2 - x1;
final float dy = y2 - y1;
final float up = dx * (y1 + y2 - y - y);
return up * up / (dx * dx + dy * dy);
}


private void computeGraph(Function f, float minX, float maxX, float minY,
float maxY, Data graph) {
if (f.arity() == 0) {
float v = (float) f.eval();
if (v < -10000f) {
v = -10000f;
}
if (v > 10000f) {
v = 10000f;
}
graph.clear();
graph.push(minX, v);
graph.push(maxX, v);
return;
}


final float scale = width / gwidth;
final float maxStep = 15.8976f / scale;
final float minStep = .05f / scale;
float ythresh = 1 / scale;
ythresh = ythresh * ythresh;
if (!graph.empty()) {
if (minX >= lastMinX) {
graph.eraseBefore(minX);
} else {
graph.eraseAfter(maxX);
maxX = Math.min(maxX, graph.firstX());
graph.swap(endGraph);
}
}
if (graph.empty()) {
graph.push(minX, eval(f, minX));
}
float leftX, leftY;
float rightX = graph.topX(), rightY = graph.topY();
int nEval = 1;
while (true) {
leftX = rightX;
leftY = rightY;
if (leftX > maxX) {
break;
}
if (next.empty()) {
float x = leftX + maxStep;
next.push(x, eval(f, x));
++nEval;
}
rightX = next.topX();
rightY = next.topY();
next.pop();


if (leftY != leftY && rightY != rightY) { // NaN
continue;
}


float dx = rightX - leftX;
float middleX = (leftX + rightX) / 2;
float middleY = eval(f, middleX);
++nEval;
boolean middleIsOutside = (middleY < leftY && middleY < rightY)
|| (leftY < middleY && rightY < middleY);
if (dx < minStep) {
if (middleIsOutside) {
graph.push(rightX, Float.NaN);
}
graph.push(rightX, rightY);
continue;
}
if (middleIsOutside
&& ((leftY < minY && rightY > maxY) || (leftY > maxY && rightY < minY))) {
graph.push(rightX, Float.NaN);
graph.push(rightX, rightY);
continue;
}


if (!middleIsOutside) {


if (distance2(leftX, leftY, rightX, rightY, middleY) < ythresh) {
graph.push(rightX, rightY);
continue;
}
}
next.push(rightX, rightY);
next.push(middleX, middleY);
rightX = leftX;
rightY = leftY;
}
if (!endGraph.empty()) {
graph.append(endGraph);
}
long t2 = System.currentTimeMillis();


next.clear();
endGraph.clear();
}


private static Path path = new Path();


private Path graphToPath(Data graph) {
boolean first = true;
int size = graph.size;
float[] xs = graph.xs;
float[] ys = graph.ys;
path.rewind();
for (int i = 0; i < size; ++i) {
float y = ys[i];
float x = xs[i];
// Calculator.log("path " + x + ' ' + y);
if (y == y) { // !NaN
if (first) {
path.moveTo(x, y);
first = false;
} else {
path.lineTo(x, y);
}
} else {
first = true;
}
}
return path;
}


private static final float NTICKS = 15;


private static float stepFactor(float w) {
float f = 1;
while (w / f > NTICKS) {
f *= 10;
}
while (w / f < NTICKS / 10) {
f /= 10;
}
float r = w / f;
if (r < NTICKS / 5) {
return f / 5;
} else if (r < NTICKS / 2) {
return f / 2;
} else {
return f;
}
}


private static StringBuilder b = new StringBuilder();
private static char[] buf = new char[20];


private static StringBuilder format(float fv) {
int pos = 0;
boolean addDot = false;
int v = Math.round(fv * 100);
boolean isNeg = v < 0;
v = isNeg ? -v : v;
for (int i = 0; i < 2; ++i) {
int digit = v % 10;
v /= 10;
if (digit != 0 || addDot) {
buf[pos++] = (char) ('0' + digit);
addDot = true;
}
}
if (addDot) {
buf[pos++] = '.';
}
if (v == 0) {
buf[pos++] = '0';
}
while (v != 0) {
buf[pos++] = (char) ('0' + (v % 10));
v /= 10;
}
if (isNeg) {
buf[pos++] = '-';
}
b.setLength(0);
b.append(buf, 0, pos);
b.reverse();
return b;
}


private void drawGraph(Canvas canvas) {
long t1 = System.currentTimeMillis();
float minX = currentX - gwidth / 2;
float maxX = minX + gwidth;
float ywidth = gwidth * height / width;
float minY = currentY - ywidth / 2;
float maxY = minY + ywidth;
if (minY < boundMinY || maxY > boundMaxY) {
float halfw = ywidth / 2;
boundMinY = minY - halfw;
boundMaxY = maxY + halfw;
clearAllGraph();
}


canvas.drawColor(0xff000000);


paint.setStrokeWidth(0);
paint.setAntiAlias(false);
paint.setStyle(Paint.Style.STROKE);


final float h2 = height / 2f;
final float scale = width / gwidth;


float x0 = -minX * scale;
boolean drawYAxis = true;
if (x0 < 25) {
x0 = 25;
// drawYAxis = false;
} else if (x0 > width - 3) {
x0 = width - 3;
// drawYAxis = false;
}
float y0 = maxY * scale;
if (y0 < 3) {
y0 = 3;
} else if (y0 > height - 15) {
y0 = height - 15;
}


final float tickSize = 3;
final float y2 = y0 + tickSize;
paint.setColor(COL_GRID);
float step = stepFactor(gwidth);
float v = ((int) (minX / step)) * step;
textPaint.setColor(COL_TEXT);
textPaint.setTextSize(12);
textPaint.setTextAlign(Paint.Align.CENTER);
float stepScale = step * scale;
for (float x = (v - minX) * scale; x <= width; x += stepScale, v += step) {
canvas.drawLine(x, 0, x, height, paint);
if (!(-.001f < v && v < .001f)) {
StringBuilder b = format(v);
canvas.drawText(b, 0, b.length(), x, y2 + 10, textPaint);
}
}


final float x1 = x0 - tickSize;
v = ((int) (minY / step)) * step;
textPaint.setTextAlign(Paint.Align.RIGHT);
for (float y = height - (v - minY) * scale; y >= 0; y -= stepScale, v += step) {
canvas.drawLine(0, y, width, y, paint);
if (!(-.001f < v && v < .001f)) {
StringBuilder b = format(v);
canvas.drawText(b, 0, b.length(), x1, y + 4, textPaint);
}
}


paint.setColor(COL_AXIS);
if (drawYAxis) {
canvas.drawLine(x0, 0, x0, height, paint);
}
canvas.drawLine(0, y0, width, y0, paint);


matrix.reset();
matrix.preTranslate(-currentX, -currentY);
matrix.postScale(scale, -scale);
matrix.postTranslate(width / 2, height / 2);


paint.setStrokeWidth(0);
paint.setAntiAlias(false);


int n = Math.min(funcs.size(), GRAPHS_SIZE);
for (int i = 0; i < n; ++i) {
computeGraph(funcs.get(i), minX, maxX, boundMinY, boundMaxY,
graphs[i]);
Path path = graphToPath(graphs[i]);
path.transform(matrix);
paint.setColor(COL_GRAPH[i]);
canvas.drawPath(path, paint);
}
lastMinX = minX;
}


private boolean canZoomIn() {
return gwidth > 1f;
}


private boolean canZoomOut() {
return gwidth < 50;
}


private void invalidateGraphs() {
clearAllGraph();
boundMinY = boundMaxY = 0;
invalidate();
}


@Override
public boolean onTouchEvent(MotionEvent event) {
return touchHandler != null ? touchHandler.onTouchEvent(event) : super
.onTouchEvent(event);
}


public void onTouchDown(float x, float y) {
zoomController.setVisible(true);
if (!scroller.isFinished()) {
scroller.abortAnimation();
}
lastTouchX = x;
lastTouchY = y;
}


public void onTouchMove(float x, float y) {
float deltaX = x - lastTouchX;
float deltaY = y - lastTouchY;
if (deltaX < -1 || deltaX > 1 || deltaY < -1 || deltaY > 1) {
scroll(-deltaX, deltaY);
lastTouchX = x;
lastTouchY = y;
invalidate();
}
}


public void onTouchUp(float x, float y) {
final float scale = width / gwidth;
float sx = -touchHandler.velocityTracker.getXVelocity();
float sy = touchHandler.velocityTracker.getYVelocity();
final float asx = Math.abs(sx);
final float asy = Math.abs(sy);
if (asx < asy / 3) {
sx = 0;
} else if (asy < asx / 3) {
sy = 0;
}
scroller.fling(Math.round(currentX * scale),
Math.round(currentY * scale), Math.round(sx), Math.round(sy),
-10000, 10000, -10000, 10000);
invalidate();
}


public void onTouchZoomDown(float x1, float y1, float x2, float y2) {
zoomTracker.start(gwidth, x1, y1, x2, y2);
}


public void onTouchZoomMove(float x1, float y1, float x2, float y2) {
if (!zoomTracker.update(x1, y1, x2, y2)) {
return;
}
float targetGwidth = zoomTracker.value;
if (targetGwidth > .25f && targetGwidth < 200) {
gwidth = targetGwidth;
}
invalidateGraphs();
}


private void scroll(float deltaX, float deltaY) {
final float scale = gwidth / width;
float dx = deltaX * scale;
float dy = deltaY * scale;
final float adx = Math.abs(dx);
final float ady = Math.abs(dy);
if (adx < ady / 3) {
dx = 0;
} else if (ady < adx / 3) {
dy = 0;
}
currentX += dx;
currentY += dy;
}
}

XML 编辑器的错误日志

java.lang.NullPointerException
at android.widget.ZoomButtonsController.createContainer(ZoomButtonsController.java:266)
at android.widget.ZoomButtonsController.<init>(ZoomButtonsController.java:212)
at calculator.GraphView.<init>(GraphView.java:43)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(    at sun.reflect.NativeConstructorAccessorImpl.newInstance(    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(    at java.lang.reflect.Constructor.newInstance(    at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.instantiateClass(ProjectCallback.java:422)
at com.android.ide.eclipse.adt.internal.editors.layout.ProjectCallback.loadView(ProjectCallback.java:179)
at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:207)
at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:135)
at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:746)
at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:64)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:718)
at android.view.LayoutInflater.inflate(LayoutInflater.java:489)
at android.view.LayoutInflater.inflate(LayoutInflater.java:372)