我正在开发一款听力测试的Android应用程序。它已经过时了，所以我不得不更新它。我使用了Sherlock库，因此该应用程序兼容许多不同的手机。我要做的是让听力测试的结果显示出来。当我绘制图形以向用户展示它们的效果时，我得到的问题是，我得到一个空指针异常。
测试完成后，用户将进入下面显示的已保存测试活动：
public class SavedResultsActivity extends SherlockListActivity {
// TODO set column names when saving test implemented
private static final String TEST_NAME_COLUMN = ResultsDatabase.SAVED_NAME;
private static final String TEST_DATE_COLUMN = ResultsDatabase.COLUMN_NAME_CREATE_DATE;
private ResultsDatabase mDb;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mDb = new ResultsDatabase(this);
setContentView(R.layout.saved_tests);
ActionBar ab = getSherlock().getActionBar();
SherlockHelper.setupActionBar(ab, this);
TextView titleText = (TextView)findViewById(R.id.title_text);
titleText.setText(R.string.Saved_Tests);
// Set the empty view
getListView().setEmptyView(findViewById(R.id.empty));
getListView().setItemsCanFocus(true);
// Get a cursor with all phones
Cursor c = getSavedTests();
if ( c != null ) {
// Set up our adapter
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
R.layout.saved_results_item, c,
new String[] { TEST_NAME_COLUMN, TEST_DATE_COLUMN, TEST_DATE_COLUMN },
new int[] { android.R.id.text1, android.R.id.text2, R.id.delete_button });
adapter.setViewBinder(mViewBinder);
// Set up our adapter
setListAdapter(adapter);
}
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id)
{
Intent intent = new Intent(this, TabbedResults.class);
Cursor cursor = (Cursor) getListAdapter().getItem(position);
intent.putExtra(ResultsDatabase._ID, cursor.getInt(cursor.getColumnIndex(ResultsDatabase._ID)));
startActivity(intent);
}
private final ViewBinder mViewBinder = new SimpleCursorAdapter.ViewBinder(){
@Override
public boolean setViewValue(View view, Cursor cursor, int columnIndex) {
if ( view.getId() == android.R.id.text1 ){
String name = cursor.getString(columnIndex);
TextView nameView = (TextView)view;
nameView.setText(name);
} else if ( view.getId() == android.R.id.text2 ){
long date = cursor.getLong(columnIndex);
String dateStr = DateUtils.formatDateTime(view.getContext(), date, DateUtils.FORMAT_SHOW_YEAR | DateUtils.FORMAT_SHOW_DATE);
TextView dateView = (TextView)view;
dateView.setText(dateStr);
} else if ( view.getId() == R.id.delete_button ){
int idCol = cursor.getColumnIndex(ResultsDatabase._ID);
final long id = cursor.getLong(idCol);
view.setOnClickListener( new OnClickListener(){
@Override
public void onClick(View v) {
deleteTest(id);
}
});
}
return true;
}
};
private static final String DELETE_SELECTION = ResultsDatabase._ID + " = ? ";
private void deleteTest(long id) {
String[] whereArgs = new String[]{String.valueOf(id)};
SQLiteDatabase db = mDb.getWritableDatabase();
db.delete(ResultsDatabase.TABLE_NAME, DELETE_SELECTION, whereArgs);
SimpleCursorAdapter adapter = (SimpleCursorAdapter) getListAdapter();
adapter.getCursor().requery();
adapter.notifyDataSetChanged();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
return MenuActivity.createMenu(this, menu);
}
// TODO fetch list of saved tests
private Cursor getSavedTests(){
// get cursor
SQLiteDatabase db = mDb.getReadableDatabase();
Cursor c = db.query(ResultsDatabase.TABLE_NAME, null, null, null, null, null,null);
startManagingCursor(c);
return c;
}
}
此处，用户将点击他们想要查看的测试，这将使用户进入选项卡式结果页面，一个标签用于另一个耳朵，另一个标签用于另一个耳朵。我已经用过碎片了：
public class TabbedResults extends SherlockFragmentActivity{
TabHost mTabHost;
TabManager mTabManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab_indicator);
ActionBar ab = this.getSupportActionBar();
SherlockHelper.setupActionBar(ab, this);
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
mTabManager = new TabManager(this, mTabHost, R.id.realtabcontent);
mTabManager.addTab(mTabHost.newTabSpec(getString(R.string.Left_ear)).setIndicator(getString(R.string.Left_ear)),
ResultActivity.Results.class, null);
mTabManager.addTab(mTabHost.newTabSpec("contacts").setIndicator(getString(R.string.Left_ear)),
ResultActivity.Results.class, null);
if (savedInstanceState != null) {
mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("tab", mTabHost.getCurrentTabTag());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
return MenuActivity.createMenu(this, menu);
}
}
此方法使用另一个名为TabManager的方法来管理打开的选项卡等：
public class TabManager extends SherlockFragmentActivity implements TabHost.OnTabChangeListener {
private final FragmentActivity mActivity;
private final TabHost mTabHost;
private final int mContainerId;
private final HashMap<String, TabInfo> mTabs = new HashMap<String, TabInfo>();
TabInfo mLastTab;
static final class TabInfo {
private final String tag;
private final Class<?> clss;
private final Bundle args;
private Fragment fragment;
TabInfo(String _tag, Class<?> _class, Bundle _args) {
tag = _tag;
clss = _class;
args = _args;
}
}
static class DummyTabFactory implements TabHost.TabContentFactory {
private final Context mContext;
public DummyTabFactory(Context context) {
mContext = context;
}
@Override
public View createTabContent(String tag) {
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
public TabManager(FragmentActivity activity, TabHost tabHost, int containerId) {
mActivity = activity;
mTabHost = tabHost;
mContainerId = containerId;
mTabHost.setOnTabChangedListener(this);
}
public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args) {
tabSpec.setContent(new DummyTabFactory(mActivity));
String tag = tabSpec.getTag();
TabInfo info = new TabInfo(tag, clss, args);
// Check to see if we already have a fragment for this tab, probably
// from a previously saved state. If so, deactivate it, because our
// initial state is that a tab isn't shown.
info.fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);
if (info.fragment != null && !info.fragment.isDetached()) {
FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
ft.detach(info.fragment);
ft.commit();
}
mTabs.put(tag, info);
mTabHost.addTab(tabSpec);
}
@Override
public void onTabChanged(String tabId) {
TabInfo newTab = mTabs.get(tabId);
if (mLastTab != newTab) {
FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
if (mLastTab != null) {
if (mLastTab.fragment != null) {
ft.detach(mLastTab.fragment);
}
}
if (newTab != null) {
if (newTab.fragment == null) {
newTab.fragment = Fragment.instantiate(mActivity,
newTab.clss.getName(), newTab.args);
ft.add(mContainerId, newTab.fragment, newTab.tag);
} else {
ft.attach(newTab.fragment);
}
}
mLastTab = newTab;
ft.commit();
mActivity.getSupportFragmentManager().executePendingTransactions();
}
}
private Intent createIntent( boolean aRight) {
Intent newIntent = new Intent(getIntent());
newIntent.putExtra(ResultActivity.IS_RIGHT_EAR, aRight);
newIntent.setClass(this, ResultActivity.class);
return newIntent;
}
}
因此，用于显示每只耳朵结果的活动是结果活动：
public class ResultActivity extends SherlockFragmentActivity {
public static final String IS_RIGHT_EAR = "is_right_ear";
private ArrayList<EarSrt> leftAnswerList;
private ArrayList<EarSrt> rightAnswerList;
private boolean isRightEarTab = true;
private boolean bothEarsBad;
private boolean leftEarBad;
private boolean rightEarBad;
@SuppressWarnings("unchecked")
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.result);
Intent intent = getIntent();
int rowId = intent.getIntExtra(ResultsDatabase._ID, -1);
if ( rowId != -1 ) {
ResultsDatabase db = new ResultsDatabase(this);
String select = "(" + ResultsDatabase._ID + " == " + rowId + ")";
Cursor c = db.getReadableDatabase().query(ResultsDatabase.TABLE_NAME, null, select, null, null, null,null);
if ( c.moveToFirst() ) {
int leftEarColumn = c.getColumnIndex(ResultsDatabase.LEFT_EAR);
byte[] leftEarByteArray = c.getBlob(leftEarColumn);
int rightEarColumn = c.getColumnIndex(ResultsDatabase.RIGHT_EAR);
byte[] rightEarByteArray = c.getBlob(rightEarColumn);
leftAnswerList = (ArrayList<EarSrt>) ResultsDatabase.deserializeObject(leftEarByteArray);
rightAnswerList = (ArrayList<EarSrt>) ResultsDatabase.deserializeObject(rightEarByteArray);
}
} else {
byte[] leftEarByteArray = getIntent().getByteArrayExtra(ResultsDatabase.LEFT_EAR);
byte[] rightEarByteArray = getIntent().getByteArrayExtra(ResultsDatabase.RIGHT_EAR);
leftAnswerList = (ArrayList<EarSrt>) ResultsDatabase.deserializeObject(leftEarByteArray);
rightAnswerList = (ArrayList<EarSrt>) ResultsDatabase.deserializeObject(rightEarByteArray);
}
isRightEarTab = getIntent().getBooleanExtra(IS_RIGHT_EAR, true);
setResults(leftAnswerList, rightAnswerList);
if (savedInstanceState == null) {
// Do first time initialization -- add initial fragment.
Fragment newFragment = new Results();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(R.id.resultsContainer, newFragment).commit();
}
}
private float calculateAverage(List<EarSrt> steps) {
float srt = 0.0f;
int length = steps.size();
for (int i = (int)Math.ceil( (float)length/(float)2); i < length; i++) {
EarSrt es = steps.get(i);
srt += es.getSrt();
//printf("%f ," , [es srt]);
}
srt = srt / (length-(float)Math.ceil( (float)length/(float)2));
// printf("\n%f\n" , srt);
return srt;
}
private void setResults(List<EarSrt> leftEar, List<EarSrt> rightEar) {
float esLeft = calculateAverage(leftEar);
float esRight = calculateAverage(rightEar);
leftEarBad = (esLeft > 24.0);
rightEarBad = (esRight > 24.0);
bothEarsBad = (leftEarBad && rightEarBad);
setResultCaption(bothEarsBad, leftEarBad, rightEarBad);
}
/**
* TODO: this needs finishing
*/
private void setResultCaption(boolean bothEarsBad, boolean leftEarBad, boolean rightEarBad) {
TextView resultsTextView = (TextView)findViewById(R.id.results_text);
StringBuilder resultsText = new StringBuilder();
if (bothEarsBad) {
resultsText.append(getString(R.string.The_test_indicates_a_possible_hearing_loss));
resultsText.append(getString(R.string.We_recommend_that_you_visit_a_Hearing_Care_Professional_for_a_comprehensive_hearing_check));
}else{
if (leftEarBad) {
resultsText.append(getString(R.string.The_test_indicates_a_possible_hearing_loss_for_your_left_ear));
resultsText.append(getString(R.string.We_recommend_that_you_visit_a_Hearing_Care_Professional_for_a_comprehensive_hearing_check));
} else if (rightEarBad) {
resultsText.append(getString(R.string.The_test_indicates_a_possible_hearing_loss_for_your_Right_ear));
resultsText.append(getString(R.string.We_recommend_that_you_visit_a_Hearing_Care_Professional_for_a_comprehensive_hearing_check));
}else {
resultsText.append(getString(R.string.There_is_no_indication_of_hearing_loss));
}
}
resultsText.append(getString(R.string.The_results_of_the__hearing_test_are_not_to_be_utilized_as_an_official_outcome_for_assessing_levels_of_hearing_loss_True_hearing_loss_assessments_can_only_be_determined_by_a_licensed_hearing_healthcare_provider));
resultsTextView.setText(resultsText.toString());
}
public void goToLocate(View aView){
Intent locate = new Intent( this, MapActivity.class);
startActivity(locate);
finish();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
return MenuActivity.createMenu(this, menu);
}
public static class Results extends SherlockFragment{
// @Override
// public void onCreate(Bundle savedInstanceState){
// super.onCreate(savedInstanceState);
//
// }
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.results_layout, container, false);
return rootView;
}
}
}
现在这个类使用GraphView类绘制图形：
public final class GraphView extends View {
private static final float SCALE = 0.008f; // map (min,max) to ( 0, 1)
private static final float WIDTH = 0.02f; // map (min,max) to ( 0, 1)
ArrayList<EarSrt> mPoints;
// drawing tools
private RectF rimRect;
private RectF rimRectTop;
private RectF rimRectBottom;
private float[] centreLine;
private RectF topSideBar;
private RectF bottomSideBar;
private Paint rimPaintTop;
private Paint rimPaintBottom;
private Paint outerRimPaint;
private Paint centreLinePaint;
private Paint topSideBarPaint;
private Paint bottomSideBarPaint;
private Paint titlePaint;
private Paint keyPaint;
private Paint correctPointPaint;
private Paint incorrectPointPaint;
private Paint linePaint;
private Paint pointOutlinePaint;
private Paint averagePaint;
private Paint backgroundPaint;
// end drawing tools
private Bitmap background; // holds the cached static part
private float mAverage;
public GraphView(Context context) {
super(context);
init();
}
public GraphView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public GraphView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init();
}
private void init() {
initDrawingTools();
}
private String getTitle() {
return getContext().getString(R.string.Normal_hearing);
}
private void initDrawingTools() {
rimRect = new RectF(0.0f, 0.0f, 1.0f, 1.0f);
rimRectTop = new RectF(0.0f, 0.5f, 1.0f, 1.0f);
rimRectBottom = new RectF(0.0f, 0.0f, 1.0f, 0.5f);
centreLine = new float[4];
centreLine[0]=0.0f;
centreLine[1]=0.5f;
centreLine[2]=1.0f;
centreLine[3]=0.5f;
topSideBar = new RectF(0.95f, 0.5f, 1.0f, 1.0f);
bottomSideBar = new RectF(0.95f, 0.0f, 1.0f, 0.5f);
// the linear gradient is a bit skewed for realism
rimPaintTop = new Paint();
rimPaintTop.setFlags(Paint.ANTI_ALIAS_FLAG);
rimPaintTop.setShader(new LinearGradient(0.40f, 0.0f, 0.60f, 1.0f,
0xff9ea3ac,
0xffc0c2c6,
TileMode.CLAMP));
rimPaintBottom = new Paint();
rimPaintBottom.setFlags(Paint.ANTI_ALIAS_FLAG);
rimPaintBottom.setShader(new LinearGradient(0.40f, 0.0f, 0.60f, 1.0f,
0xffc5cbbd,
0xff3d4649,
TileMode.CLAMP));
outerRimPaint = new Paint();
outerRimPaint.setAntiAlias(true);
outerRimPaint.setStyle(Paint.Style.STROKE);
outerRimPaint.setColor(Color.argb(0x4f, 0x33, 0x36, 0x33));
outerRimPaint.setStrokeWidth(0.001f);
centreLinePaint = new Paint();
centreLinePaint.setStyle(Paint.Style.STROKE);
centreLinePaint.setColor(0xff90cc38);
centreLinePaint.setAntiAlias(true);
centreLinePaint.setStrokeWidth(0.02f);
topSideBarPaint = new Paint();
topSideBarPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
topSideBarPaint.setShader(new LinearGradient(0.40f, 0.0f, 0.60f, 1.0f,
0xffc5cbbd,
0xff3d4649,
TileMode.CLAMP));
bottomSideBarPaint = new Paint();
bottomSideBarPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
bottomSideBarPaint.setShader(new LinearGradient(0.40f, 0.0f, 0.60f, 1.0f,
0xff4c9b3e,
0xffa0dd61,
TileMode.CLAMP));
titlePaint = new Paint();
titlePaint.setColor(0xffffffff);
titlePaint.setAntiAlias(true);
titlePaint.setTypeface(Typeface.DEFAULT_BOLD);
titlePaint.setTextAlign(Paint.Align.CENTER);
titlePaint.setTextSize(0.05f);
titlePaint.setTextScaleX(0.8f);
keyPaint = new Paint();
keyPaint.setColor(0xff000000);
keyPaint.setAntiAlias(true);
keyPaint.setTypeface(Typeface.DEFAULT_BOLD);
keyPaint.setTextAlign(Paint.Align.LEFT);
keyPaint.setTextSize(0.05f);
keyPaint.setTextScaleX(0.8f);
backgroundPaint = new Paint();
backgroundPaint.setFilterBitmap(true);
linePaint = new Paint();
linePaint.setColor(0xffffffff);
linePaint.setStrokeWidth(0);
averagePaint = new Paint();
averagePaint.setColor(0xff000000);
averagePaint.setStyle(Paint.Style.FILL);
correctPointPaint = new Paint();
correctPointPaint.setColor(0xff90cc38);
correctPointPaint.setStyle(Paint.Style.FILL);
incorrectPointPaint = new Paint();
incorrectPointPaint.setColor(0xffb1b3ba);
correctPointPaint.setStyle(Paint.Style.FILL);
pointOutlinePaint = new Paint();
pointOutlinePaint.setStyle(Paint.Style.STROKE);
pointOutlinePaint.setColor(0xffffffff);
pointOutlinePaint.setAntiAlias(true);
pointOutlinePaint.setStrokeWidth(0.0f);
}
private void drawRim(Canvas canvas) {
// first, draw the metallic body
canvas.drawRect(rimRectTop, rimPaintTop);
canvas.drawRect(rimRectBottom, rimPaintBottom);
// now the outer rim circle
canvas.drawRect(rimRect, outerRimPaint);
// Draw middleline
canvas.drawLines(centreLine, centreLinePaint);
// Draw sidebars
canvas.drawRect(topSideBar, topSideBarPaint);
canvas.drawRect(bottomSideBar, bottomSideBarPaint);
}
public void setPoints( ArrayList<EarSrt> aPoints){
mPoints = aPoints;
}
private void drawTitle(Canvas canvas) {
String title = getTitle();
canvas.drawText(title, 0.2f, 0.1f, titlePaint);
}
private void drawBackground(Canvas canvas) {
if (background == null) {
} else {
canvas.drawBitmap(background, 0, 0, backgroundPaint);
}
}
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// We purposely disregard child measurements because act as a
// wrapper to a SurfaceView that centers the camera preview instead
// of stretching it.
final int width = resolveSize(getSuggestedMinimumWidth(), widthMeasureSpec);
final int height = (int)(width * 0.8f);
setMeasuredDimension(width, height);
}
@Override
protected void onDraw(Canvas canvas) {
drawBackground(canvas);
canvas.restore();
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
regenerateBackground();
}
private void regenerateBackground() {
// free the old bitmap
if (background != null) {
background.recycle();
}
background = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
Canvas backgroundCanvas = new Canvas(background);
float scaleWidth = (float) getWidth();
float scaleHeight = (float) getHeight();
backgroundCanvas.scale(scaleWidth, scaleHeight/1.23f);
drawRim(backgroundCanvas);
drawTitle(backgroundCanvas);
drawPoints(backgroundCanvas);
drawKey(backgroundCanvas);
}
private void drawPoints(Canvas canvas) {
float gap = 1.0f/((float)mPoints.size()+2);
// Iterate though the points twice, once to
// draw the line and one to draw the points
// doesn't appear to be the most efficient
// method, but calculations of point size etc
// Draw line
int count = 1;
float prev_x = 0.0f;
float prev_y = 0.0f;
for ( EarSrt vo : mPoints){
float y_pos = 0.5f + 2*( vo.getSrt() - 24.0f)*SCALE;
float x_pos = gap*count;
if ( count != 1 ){
canvas.drawLine(prev_x, prev_y, x_pos, y_pos, linePaint);
}
count++;
prev_x = x_pos;
prev_y = y_pos;
}
// draw points
count = 1;
for ( EarSrt vo : mPoints){
float y_pos = 0.5f + 2*( vo.getSrt() - 24.0f)*SCALE;
float x_pos = gap*count;
count++;
RectF rect = new RectF(x_pos - WIDTH, y_pos - WIDTH, x_pos + WIDTH, y_pos + WIDTH);
if ( vo.isCorrect() ) {
canvas.drawRect(rect, correctPointPaint);
} else {
canvas.drawRect(rect, incorrectPointPaint);
}
canvas.drawRect(rect, pointOutlinePaint);
}
// Plot average line
float yAverage = 0.5f + 2*( mAverage - 24.0f)*SCALE;
RectF averageRect = new RectF(0.95f, yAverage - WIDTH/2.0f, 1.0f, yAverage + WIDTH/2.0f);
canvas.drawRect(averageRect, averagePaint);
}
private void drawKey(Canvas canvas) {
float rightEdge = 0.05f;
float leftEdge = 0.05f + 4 * WIDTH;
// Example correct square
RectF rect = new RectF(rightEdge, 1.1f - WIDTH, rightEdge + 2 * WIDTH, 1.1f + WIDTH);
canvas.drawRect(rect, correctPointPaint);
canvas.drawRect(rect, pointOutlinePaint);
String correctResults = getContext().getString(R.string.Correct_results);
canvas.drawText(correctResults, leftEdge, 1.1f + WIDTH, keyPaint);
// Test result line
RectF averageRect = new RectF(rightEdge, 1.2f - WIDTH/2.0f, rightEdge + 2 * WIDTH, 1.2f + WIDTH/2.0f);
canvas.drawRect(averageRect, averagePaint);
String testResults = getContext().getString(R.string.Your_test_result);
canvas.drawText(testResults, leftEdge, 1.2f + WIDTH/2.0f, keyPaint);
}
public void setAverage(float aAverage) {
mAverage = aAverage;
}
}
我得到的问题是在drawPoints，regenerateBackground和onSizeChanged方法的GraphView类上。
我遇到的另一个问题是在正确的标签中显示正确的信息。因此，对于一个选项卡，它仅显示左侧的结果，反之亦然。任何有关这些问题的帮助都会非常感激，因为我一直试图让这个问题长期存在!!
再次感谢您给予的任何帮助。