我是Java的新手，对Android开发来说真的很陌生。 我正在尝试制作摩尔斯电码应用程序，它将在设备的屏幕上闪烁用户在摩尔斯电码中输入的消息。 我的问题是我找不到暂停代码的方法来定时。 我知道将wait（）或sleep（）直接放入是不可能的。在网上搜索之后，我找到了一些代码并将其实现到我的中 - 这是当前的代码 - 这只是一个倒计时来测试等待：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_flash);
// ALL THIS STUFF IS AUTO-GENERATED
final View controlsView = findViewById(R.id.fullscreen_content_controls);
final View contentView = findViewById(R.id.fullscreen_content);
// Set up an instance of SystemUiHider to control the system UI for
// this activity.
mSystemUiHider = SystemUiHider.getInstance(this, contentView, HIDER_FLAGS);
mSystemUiHider.setup();
mSystemUiHider
.setOnVisibilityChangeListener(new SystemUiHider.OnVisibilityChangeListener() {
// Cached values.
int mControlsHeight;
int mShortAnimTime;
@Override
@TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
public void onVisibilityChange(boolean visible) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
// If the ViewPropertyAnimator API is available
// (Honeycomb MR2 and later), use it to animate the
// in-layout UI controls at the bottom of the
// screen.
if (mControlsHeight == 0) {
mControlsHeight = controlsView.getHeight();
}
if (mShortAnimTime == 0) {
mShortAnimTime = getResources().getInteger(
android.R.integer.config_shortAnimTime);
}
controlsView.animate()
.translationY(visible ? 0 : mControlsHeight)
.setDuration(mShortAnimTime);
} else {
// If the ViewPropertyAnimator APIs aren't
// available, simply show or hide the in-layout UI
// controls.
controlsView.setVisibility(visible ? View.VISIBLE : View.GONE);
}
if (visible && AUTO_HIDE) {
// Schedule a hide().
delayedHide(AUTO_HIDE_DELAY_MILLIS);
}
}
});
// Set up the user interaction to manually show or hide the system UI.
contentView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (TOGGLE_ON_CLICK) {
mSystemUiHider.toggle();
} else {
mSystemUiHider.show();
}
}
});
// Upon interacting with UI controls, delay any scheduled hide()
// operations to prevent the jarring behavior of controls going away
// while interacting with the UI.
// EVERYTHING UP TO HERE IS AUTO-GENERATED
final TextView currentLabel = (TextView) findViewById(R.id.labelCurrent);
final TextView totalLabel = (TextView) findViewById(R.id.labelTotal);
new Thread () {
public void run() {
currentLabel.setText("3");
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
currentLabel.setText("2");
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
currentLabel.setText("1");
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
startActivity(new Intent(getApplicationContext(), MainActivity.class));
}
}.start();
}
在测试此代码时，我发现在模拟的AVD中，它直接回到MainActivity，当我生成一个APK并在我的设备上测试它时，应用程序崩溃了。
感谢任何帮助。
编辑1-这是logcat：
08-09 15:42:29.054 2012-2012/com.example.nat.morseflasher D/gralloc_goldfish﹕ Emulator without GPU emulation detected.
08-09 15:42:38.564 2012-2012/com.example.nat.morseflasher D/dalvikvm﹕ GC_FOR_ALLOC freed 143K, 8% free 3195K/3444K, paused 142ms, total 183ms
08-09 15:42:55.654 2012-2012/com.example.nat.morseflasher I/Choreographer﹕ Skipped 31 frames! The application may be doing too much work on its main thread.
08-09 15:42:56.294 2012-2012/com.example.nat.morseflasher I/Choreographer﹕ Skipped 47 frames! The application may be doing too much work on its main thread.
08-09 15:43:07.725 2012-2012/com.example.nat.morseflasher I/Choreographer﹕ Skipped 1159 frames! The application may be doing too much work on its main thread.
编辑2：
好的，所以我已经实现了你提供给我的代码，虽然我改变了一些东西，所以它符合我的要求。
当我尝试运行时，日志会显示“正在启动摩尔斯电码闪光灯...”消息，但它永远不会出现在打印字母或符号部分。当我点击就绪按钮时，根本没有任何变化，它只是回到onPostExecute函数中定义的主要活动。
这是XML：
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#0099cc"
tools:context="com.example.nat.morseflasher.FlashActivity">
<!-- The primary full-screen view. This can be replaced with whatever view
is needed to present your content, e.g. VideoView, SurfaceView,
TextureView, etc. -->
<TextView android:id="@+id/fullscreen_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:keepScreenOn="true"
android:textColor="#33b5e5"
android:textStyle="bold"
android:textSize="50sp"
android:gravity="center"
android:text="@string/dummy_content"
android:background="#000000" />
<!-- This FrameLayout insets its children based on system windows using
android:fitsSystemWindows. -->
<FrameLayout android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:background="#000000"
android:id="@+id/frameLayout">
<LinearLayout android:id="@+id/fullscreen_content_controls"
style="?metaButtonBarStyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom|center_horizontal"
android:background="@color/black_overlay"
android:orientation="horizontal"
tools:ignore="UselessParent">
</LinearLayout>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="-"
android:id="@+id/labelCurrent"
android:layout_gravity="center"
android:layout_marginBottom="40dp"
android:textSize="100sp"
android:textColor="#ffffff" />
<TextView
android:layout_width="fill_parent"
android:layout_height="60dp"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="Ready?"
android:id="@+id/labelTotal"
android:layout_gravity="center"
android:layout_marginTop="40dp"
android:textSize="25sp"
android:gravity="center_horizontal"
android:textIsSelectable="false"
android:textColor="#ffffff" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/tapToGo"
android:id="@+id/buttonGo"
android:layout_gravity="center_horizontal|bottom"
android:layout_marginBottom="35dp"
android:onClick="doMorse" />
</FrameLayout>
</FrameLayout>
这是java：
package com.example.nat.morseflasher;
import com.example.nat.morseflasher.util.SystemUiHider;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.TextView;
/**
* An example full-screen activity that shows and hides the system UI (i.e.
* status bar and navigation/system bar) with user interaction.
*
* @see SystemUiHider
*/
public class FlashActivity extends Activity {
/**
* Whether or not the system UI should be auto-hidden after
* {@link #AUTO_HIDE_DELAY_MILLIS} milliseconds.
*/
private static final boolean AUTO_HIDE = true;
/**
* If {@link #AUTO_HIDE} is set, the number of milliseconds to wait after
* user interaction before hiding the system UI.
*/
private static final int AUTO_HIDE_DELAY_MILLIS = 3000;
/**
* If set, will toggle the system UI visibility upon interaction. Otherwise,
* will show the system UI visibility upon interaction.
*/
private static final boolean TOGGLE_ON_CLICK = true;
/**
* The flags to pass to {@link SystemUiHider#getInstance}.
*/
private static final int HIDER_FLAGS = SystemUiHider.FLAG_HIDE_NAVIGATION;
/**
* The instance of the {@link SystemUiHider} for this activity.
*/
private SystemUiHider mSystemUiHider;
private final static String TAG = "FlashActivity";
private final static long TIME_UNIT = 250L;
private final static long ONE_SECOND = 1000L;
private final static long DOT_DELAY = TIME_UNIT;
private final static long DASH_DELAY = TIME_UNIT * 2;
private final static long INTRA_LETTER_DELAY = TIME_UNIT;
private final static long INTER_LETTER_DELAY = TIME_UNIT * 2;
private final static long INTER_WORD_DELAY = TIME_UNIT * 6;
Button goButton;
FrameLayout layoutFrame;
TextView currentLabel, totalLabel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_flash);
final View controlsView = findViewById(R.id.fullscreen_content_controls);
final View contentView = findViewById(R.id.fullscreen_content);
// Set up an instance of SystemUiHider to control the system UI for
// this activity.
mSystemUiHider = SystemUiHider.getInstance(this, contentView, HIDER_FLAGS);
mSystemUiHider.setup();
mSystemUiHider
.setOnVisibilityChangeListener(new SystemUiHider.OnVisibilityChangeListener() {
// Cached values.
int mControlsHeight;
int mShortAnimTime;
@Override
@TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
public void onVisibilityChange(boolean visible) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
// If the ViewPropertyAnimator API is available
// (Honeycomb MR2 and later), use it to animate the
// in-layout UI controls at the bottom of the
// screen.
if (mControlsHeight == 0) {
mControlsHeight = controlsView.getHeight();
}
if (mShortAnimTime == 0) {
mShortAnimTime = getResources().getInteger(
android.R.integer.config_shortAnimTime);
}
controlsView.animate()
.translationY(visible ? 0 : mControlsHeight)
.setDuration(mShortAnimTime);
} else {
// If the ViewPropertyAnimator APIs aren't
// available, simply show or hide the in-layout UI
// controls.
controlsView.setVisibility(visible ? View.VISIBLE : View.GONE);
}
if (visible && AUTO_HIDE) {
// Schedule a hide().
delayedHide(AUTO_HIDE_DELAY_MILLIS);
}
}
});
// Set up the user interaction to manually show or hide the system UI.
contentView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (TOGGLE_ON_CLICK) {
mSystemUiHider.toggle();
} else {
mSystemUiHider.show();
}
}
});
goButton = (Button) findViewById(R.id.buttonGo);
layoutFrame = (FrameLayout) findViewById(R.id.frameLayout);
currentLabel = (TextView) findViewById(R.id.labelCurrent);
totalLabel = (TextView) findViewById(R.id.labelTotal);
// Upon interacting with UI controls, delay any scheduled hide()
// operations to prevent the jarring behavior of controls going away
// while interacting with the UI.
}
@Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Trigger the initial hide() shortly after the activity has been
// created, to briefly hint to the user that UI controls
// are available.
delayedHide(100);
}
/**
* Touch listener to use for in-layout UI controls to delay hiding the
* system UI. This is to prevent the jarring behavior of controls going away
* while interacting with activity UI.
*/
View.OnTouchListener mDelayHideTouchListener = new View.OnTouchListener() {
@Override
public boolean onTouch(View view, MotionEvent motionEvent) {
if (AUTO_HIDE) {
delayedHide(AUTO_HIDE_DELAY_MILLIS);
}
return false;
}
};
Handler mHideHandler = new Handler();
Runnable mHideRunnable = new Runnable() {
@Override
public void run() {
mSystemUiHider.hide();
}
};
/**
* Schedules a call to hide() in [delay] milliseconds, canceling any
* previously scheduled calls.
*/
private void delayedHide(int delayMillis) {
mHideHandler.removeCallbacks(mHideRunnable);
mHideHandler.postDelayed(mHideRunnable, delayMillis);
}
public void doMorse(View vw) {
goButton.setVisibility(View.GONE);
(new DoMorseFlashing()).execute();
}
private class DoMorseFlashing extends AsyncTask <String, Boolean, Void> {
SharedPreferences mPrefs = getSharedPreferences("MorseFlasher", Context.MODE_PRIVATE);
String msgStr, currentLetterMorse;
@Override
protected Void doInBackground(String... message) {
Log.v(TAG, "Starting Morse Code flasher...");
msgStr = mPrefs.getString("prevMsg", "");
String totalStr = "";
/*currentLabel.setText("3");
*doDelay(ONE_SECOND);
*currentLabel.setText("2");
*doDelay(ONE_SECOND);
*currentLabel.setText("1");
*doDelay(ONE_SECOND);
*/
for(int i=0; i<msgStr.length(); i++) {
if(msgStr.charAt(i)=='|') {
doDelay(INTER_WORD_DELAY);
}
else {
currentLetterMorse = convert(msgStr.charAt(i));
currentLabel.setText(msgStr.substring(i, i + 1));
totalStr += msgStr.substring(i, i + 1);
totalLabel.setText(totalStr);
Log.v(TAG, " flashing letter " + msgStr.charAt(i) + " with morse code " + currentLetterMorse + ":");
for (int j = 0; j < currentLetterMorse.length(); j++) {
Log.v(TAG, "flashing symbol " + currentLetterMorse.charAt(j) + ":");
flash(currentLetterMorse.charAt(j));
doDelay(INTRA_LETTER_DELAY);
}
doDelay(INTER_LETTER_DELAY);
}
}
return null;
}
protected void onPostExecute(Void result) {
// Set the button message back to "touch here" to indicate that were done flashing:
startActivity(new Intent(getApplicationContext(), MainActivity.class));
}
void flash(char letter) {
layoutFrame.setBackgroundColor(Color.WHITE);
currentLabel.setTextColor(Color.BLACK);
totalLabel.setTextColor(Color.BLACK);
switch (letter) {
case '.':
doDelay(DOT_DELAY);
case '-':
doDelay(DASH_DELAY);
}
layoutFrame.setBackgroundColor(Color.BLACK);
currentLabel.setTextColor(Color.WHITE);
totalLabel.setTextColor(Color.WHITE);
}
String convert(char letter){
switch (letter){
case 'a':
return ".-";
case 'b':
return "-…";
case 'c':
return "-.-.";
case 'd':
return "-..";
case 'e':
return ".";
case 'f':
return "..-.";
case 'g':
return "--.";
case 'h':
return "….";
case 'i':
return "..";
case 'j':
return ".---";
case 'k':
return "-.-";
case 'l':
return ".-..";
case 'm':
return "--";
case 'n':
return "-.";
case 'o':
return "---";
case 'p':
return ".--.";
case 'q':
return "--.-";
case 'r':
return ".-.";
case 's':
return "...";
case 't':
return "-";
case 'u':
return "..-";
case 'v':
return "...-";
case 'w':
return ".--";
case 'x':
return "-..-";
case 'y':
return "-.--";
case 'z':
return "--..";
case ' ':
return "|";
default:
return "|";
}
}
void doDelay(Long delay) {
try {
Thread.sleep(delay);
} catch (InterruptedException e) {
// Ignore interruptions
}
}
}
}
这是LogCat：
08-10 18:30:43.856 2090-2090/com.example.nat.morseflasher D/gralloc_goldfish﹕ Emulator without GPU emulation detected.
08-10 18:30:46.146 2090-2106/com.example.nat.morseflasher D/dalvikvm﹕ GC_FOR_ALLOC freed 146K, 8% free 3192K/3448K, paused 31ms, total 39ms
08-10 18:30:50.816 2090-2090/com.example.nat.morseflasher I/Choreographer﹕ Skipped 464 frames! The application may be doing too much work on its main thread.
08-10 18:31:04.116 2090-2090/com.example.nat.morseflasher I/Choreographer﹕ Skipped 69 frames! The application may be doing too much work on its main thread.
08-10 18:31:06.486 2090-2090/com.example.nat.morseflasher I/Choreographer﹕ Skipped 62 frames! The application may be doing too much work on its main thread.
08-10 18:31:11.176 2090-2090/com.example.nat.morseflasher I/Choreographer﹕ Skipped 37 frames! The application may be doing too much work on its main thread.
08-10 18:31:11.937 2090-2106/com.example.nat.morseflasher V/FlashActivity﹕ Starting Morse Code flasher...
08-10 18:31:13.437 2090-2090/com.example.nat.morseflasher I/Choreographer﹕ Skipped 109 frames! The application may be doing too much work on its main thread.
编辑3： 好的，所以早期的问题是由于它没有从SharedPreferences中检索我的字符串这一事实，所以为了确保其他所有工作，我在代码中将消息字符串设置为“test”。现在，问题是，当它改变屏幕的颜色时，我得到一个错误，说只有创建视图层次结构的主线程才能触及它的视图。
编辑4： 当我去更改屏幕和文本颜色时，我已经通过使用runOnUiThread（）修复了上述错误，现在闪烁了！
答案 0 :(得分：2)
LogCat消息告诉您，您的应用在主线程上花费了太多时间，并且处理GUI的时间不足。
如果你想要做的只是闪烁屏幕，你可以使用简单的AsyncTask而不是SystemUiHider的所有复杂性。
这里有一些代码显示了如何使用简单的线程休眠来处理时序来使用后台AsyncTask。由于它是一个后台任务，所以睡眠不会干扰主GUI线程。
主要功能是定期调用publishProgess()以打开或关闭闪光灯。请注意，您无法在doInBackground()方法堆栈中进行GUI更改，但可以在onProgessUpdate（）和onPostExecute（）中进行更改。我使用相同的按钮来启动和显示闪烁，以便我可以使用onPostExecute()方法来重置按钮文本。
您显然需要为其他字母添加莫尔斯代码字符串，并可能调整时间值以使事情看起来正确。
package com.example.com;
import android.app.Activity;
import android.graphics.Color;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends Activity {
// String for LogCat documentation
private final static String TAG = "MainActivity";
// These define the lengths for the dots, dashes, and times in between:
private final static long TIME_UNIT = 250L;
private final static long DOT_DELAY = TIME_UNIT * 2;
private final static long DASH_DELAY = TIME_UNIT * 3;
private final static long INTRA_LETTER_DELAY = TIME_UNIT;
private final static long INTER_LETTER_DELAY = TIME_UNIT * 3;
private final static long INTER_WORD_DELAY = TIME_UNIT * 7;
private Button flasher = null;
private EditText message = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
flasher = (Button) findViewById(R.id.flasher);
message = (EditText) findViewById(R.id.message);
}
public void doMorse(View vw) {
String messageStr = message.getText().toString();
if (messageStr.length() > 0) {
// This creates and starts a background task to do the flashing:
(new DoMorseFlashing()).execute(messageStr);
// Set the button message to indicate that we're flashing a message:
flasher.setText(R.string.flashing_message);
}
}
private class DoMorseFlashing extends AsyncTask <String, Boolean, Void> {
@Override
protected Void doInBackground(String... message) {
Log.v(TAG, "Starting Morse Code flasher...");
for (char letter : message[0].toCharArray()) {
if (letter == ' ')
doDelay(INTER_WORD_DELAY);
else
showLetter(letter);
}
return null;
}
protected void onProgressUpdate(Boolean... flasherOn) {
if (flasherOn[0])
flasher.setBackgroundColor(Color.BLUE);
else
flasher.setBackgroundColor(Color.WHITE);
}
protected void onPostExecute(Void result) {
// Set the button message back to "touch here" to indicate that we're done flashing:
flasher.setText(R.string.touch_here);
}
void showLetter(char letter) {
Log.v(TAG, "Flashing code for " + letter);
switch (letter) {
case 'A': showMorse(".-"); break;
case 'B': showMorse("-..."); break;
case 'C': showMorse("-.-."); break;
// cases for the other letters...
default: /* skip character */
}
doDelay(INTER_LETTER_DELAY);
}
void showMorse(String morse) {
Log.v(TAG, "Flashing code " + morse);
for (char dotDash: morse.toCharArray()) {
Log.v(TAG, "Flashing " + dotDash);
publishProgress(true);
if (dotDash == '.')
doDelay(DOT_DELAY);
else
doDelay(DASH_DELAY);
doDelay(INTRA_LETTER_DELAY);
publishProgress(false);
}
}
void doDelay(Long delay) {
try {
Thread.sleep(delay);
} catch (InterruptedException e) {
// Ignore interruptions
}
}
}
}
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<EditText
android:id="@+id/message"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:inputType="textCapCharacters"
android:hint="@string/enter_message" />
<Button
android:id="@+id/flasher"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="top|center"
android:background="@android:color/background_light"
android:hint="@string/touch_here"
android:onClick="doMorse" />
</LinearLayout>
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Morse Flasher</string>
<string name="enter_message">Enter message</string>
<string name="touch_here">Touch here to flash message</string>
<string name="flashing_message">Flashing message</string>
</resources>