Android Studio TextView.text 不更新
Android Studio TextView.text does not update
我稍微修改了MyFirstApp。我把它变成了一个方便、简单的应用程序，可以行驶里程和燃料，按下按钮后，开始新的 activity，它在 litres/100km.
[=43= 中显示燃料使用情况]
我面临的问题是无论在单击按钮之前输入什么值，输出总是显示 62,14 l/100km。我猜这是第一次计算的结果，没有更新。
strings.xml:
<resources>
<string name="app_name">FuelEcoCalc</string>
<string name="action_settings">Settings</string>
<string name="edit_miles">Distance in miles</string>
<string name="edit_litres">Fuel qty in litres</string>
<string name="button_calculate">Calculate</string>
<string name="title_activity_main">MainActivity</string>
<string name="title_activity_display_message">My Message</string>
<string name="hello_world">Hello World</string>
</resources>
menu_display_message.xml:
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context="com.example.wojtek.myfirstapp.DisplayMessageActivity">
<item android:id="@+id/action_settings" android:title="@string/action_settings"
android:orderInCategory="100" app:showAsAction="never" />
</menu>
menu_my.xml:
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" tools:context=".MyActivity">
<item android:id="@+id/action_settings" android:title="@string/action_settings"
android:orderInCategory="100" app:showAsAction="never" />
</menu>
activity_my.xml:
<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/edit_miles"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/edit_miles">
</EditText>
<EditText
android:id="@+id/edit_litres"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/edit_litres">
</EditText>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/button_calculate"
android:onClick="sendMessage">
</Button>
</LinearLayout>
activity_display_message.xml:
<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.wojtek.myfirstapp.DisplayMessageActivity">
<TextView android:text="@string/title_activity_display_message" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
MyActivity.java:
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
public class MyActivity extends ActionBarActivity {
public final static String MILES_MESSAGE = "com.mycompany.myfirstapp.MESSAGE";
public final static String FUEL_MESSAGE = "com.mycompany.myfirstapp.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_my, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/** Called when the user clicks the Send button */
public void sendMessage(View view) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editMiles = (EditText) findViewById(R.id.edit_miles);
String miles = editMiles.getText().toString();
EditText editFuel = (EditText) findViewById(R.id.edit_litres);
String fuel = editFuel.getText().toString();
intent.removeExtra(MILES_MESSAGE);
intent.removeExtra(FUEL_MESSAGE);
intent.putExtra(MILES_MESSAGE, miles);
intent.putExtra(FUEL_MESSAGE, fuel);
startActivity(intent);
}
}
DisplayMessageActivity.java:
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.TextView;
import java.text.DecimalFormat;
public class DisplayMessageActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
String miles = intent.getStringExtra(MyActivity.MILES_MESSAGE);
String fuel = intent.getStringExtra(MyActivity.FUEL_MESSAGE);
TextView textView = new TextView(this);
textView.setTextSize(40);
String message = "";
try {
double milesTravelled = Double.parseDouble(miles);
double fuelTaken = Double.parseDouble(fuel);
double mileToKm = 1.609344;
double kmTravelled = milesTravelled * mileToKm;
double fuelUsagePer100Km = (fuelTaken * 100) / kmTravelled;
DecimalFormat df = new DecimalFormat("#.##");
String output = df.format(fuelUsagePer100Km).toString();
message = output + " litres/100km";
} catch (Exception e) {
message = "Invalid input";
}
textView.setText(message);
setContentView(textView);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.wojtek.myfirstapp" >
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MyActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".DisplayMessageActivity"
android:label="@string/title_activity_display_message"
android:parentActivityName="com.example.wojtek.myfirstapp.MyActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.example.wojtek.myfirstapp.MyActivity" />
</activity>
</application>
</manifest>
非常感谢您的帮助。
编辑：
我想我还应该添加日志...
当我点击按钮时出现：
05-09 05:54:12.917 2106-2141/com.example.wojtek.myfirstapp W/EGL_emulation﹕ eglSurfaceAttrib not implemented
05-09 05:54:12.917 2106-2141/com.example.wojtek.myfirstapp W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xa64ae220, error=EGL_SUCCESS
可能是因为在 DisplayMessageActivity.java 中，您没有在布局中获得对 TextView 的引用
TextView textView = (TextView)findViewById(R.id.textView);
您还需要在布局文件中为您的 TextView 提供一个 ID。
<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.wojtek.myfirstapp.DisplayMessageActivity">
<TextView android:id="@+id/textView" android:text="@string/title_activity_display_message" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
编辑：我知道你的问题是什么。您无需执行任何其他操作。在您的 MyActivity.java 中，您已将两个字符串常量设置为相同的值。让他们与众不同。例如：
public final static String MILES_MESSAGE = "com.mycompany.myfirstapp.MESSAGEMILES";
public final static String FUEL_MESSAGE = "com.mycompany.myfirstapp.MESSAGEFUEL";
希望它现在对你有用。
尝试调试，您是否在 String miles 和 String fuel 中得到不同的值？每次你去显示 activity .. 我认为你应该通过它的 id
使用 textview
我稍微修改了MyFirstApp。我把它变成了一个方便、简单的应用程序，可以行驶里程和燃料，按下按钮后，开始新的 activity，它在 litres/100km.
[=43= 中显示燃料使用情况]
我面临的问题是无论在单击按钮之前输入什么值，输出总是显示 62,14 l/100km。我猜这是第一次计算的结果，没有更新。
strings.xml:
<resources>
<string name="app_name">FuelEcoCalc</string>
<string name="action_settings">Settings</string>
<string name="edit_miles">Distance in miles</string>
<string name="edit_litres">Fuel qty in litres</string>
<string name="button_calculate">Calculate</string>
<string name="title_activity_main">MainActivity</string>
<string name="title_activity_display_message">My Message</string>
<string name="hello_world">Hello World</string>
</resources>
menu_display_message.xml:
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context="com.example.wojtek.myfirstapp.DisplayMessageActivity">
<item android:id="@+id/action_settings" android:title="@string/action_settings"
android:orderInCategory="100" app:showAsAction="never" />
</menu>
menu_my.xml:
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" tools:context=".MyActivity">
<item android:id="@+id/action_settings" android:title="@string/action_settings"
android:orderInCategory="100" app:showAsAction="never" />
</menu>
activity_my.xml:
<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/edit_miles"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/edit_miles">
</EditText>
<EditText
android:id="@+id/edit_litres"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="@string/edit_litres">
</EditText>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/button_calculate"
android:onClick="sendMessage">
</Button>
</LinearLayout>
activity_display_message.xml:
<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.wojtek.myfirstapp.DisplayMessageActivity">
<TextView android:text="@string/title_activity_display_message" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
MyActivity.java:
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
public class MyActivity extends ActionBarActivity {
public final static String MILES_MESSAGE = "com.mycompany.myfirstapp.MESSAGE";
public final static String FUEL_MESSAGE = "com.mycompany.myfirstapp.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_my, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/** Called when the user clicks the Send button */
public void sendMessage(View view) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editMiles = (EditText) findViewById(R.id.edit_miles);
String miles = editMiles.getText().toString();
EditText editFuel = (EditText) findViewById(R.id.edit_litres);
String fuel = editFuel.getText().toString();
intent.removeExtra(MILES_MESSAGE);
intent.removeExtra(FUEL_MESSAGE);
intent.putExtra(MILES_MESSAGE, miles);
intent.putExtra(FUEL_MESSAGE, fuel);
startActivity(intent);
}
}
DisplayMessageActivity.java:
import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.widget.TextView;
import java.text.DecimalFormat;
public class DisplayMessageActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Intent intent = getIntent();
String miles = intent.getStringExtra(MyActivity.MILES_MESSAGE);
String fuel = intent.getStringExtra(MyActivity.FUEL_MESSAGE);
TextView textView = new TextView(this);
textView.setTextSize(40);
String message = "";
try {
double milesTravelled = Double.parseDouble(miles);
double fuelTaken = Double.parseDouble(fuel);
double mileToKm = 1.609344;
double kmTravelled = milesTravelled * mileToKm;
double fuelUsagePer100Km = (fuelTaken * 100) / kmTravelled;
DecimalFormat df = new DecimalFormat("#.##");
String output = df.format(fuelUsagePer100Km).toString();
message = output + " litres/100km";
} catch (Exception e) {
message = "Invalid input";
}
textView.setText(message);
setContentView(textView);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.wojtek.myfirstapp" >
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MyActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".DisplayMessageActivity"
android:label="@string/title_activity_display_message"
android:parentActivityName="com.example.wojtek.myfirstapp.MyActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.example.wojtek.myfirstapp.MyActivity" />
</activity>
</application>
</manifest>
非常感谢您的帮助。
编辑： 我想我还应该添加日志... 当我点击按钮时出现：
05-09 05:54:12.917 2106-2141/com.example.wojtek.myfirstapp W/EGL_emulation﹕ eglSurfaceAttrib not implemented
05-09 05:54:12.917 2106-2141/com.example.wojtek.myfirstapp W/OpenGLRenderer﹕ Failed to set EGL_SWAP_BEHAVIOR on surface 0xa64ae220, error=EGL_SUCCESS
可能是因为在 DisplayMessageActivity.java 中，您没有在布局中获得对 TextView 的引用
TextView textView = (TextView)findViewById(R.id.textView);
您还需要在布局文件中为您的 TextView 提供一个 ID。
<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.wojtek.myfirstapp.DisplayMessageActivity">
<TextView android:id="@+id/textView" android:text="@string/title_activity_display_message" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
编辑：我知道你的问题是什么。您无需执行任何其他操作。在您的 MyActivity.java 中，您已将两个字符串常量设置为相同的值。让他们与众不同。例如：
public final static String MILES_MESSAGE = "com.mycompany.myfirstapp.MESSAGEMILES";
public final static String FUEL_MESSAGE = "com.mycompany.myfirstapp.MESSAGEFUEL";
希望它现在对你有用。
尝试调试，您是否在 String miles 和 String fuel 中得到不同的值？每次你去显示 activity .. 我认为你应该通过它的 id
使用 textview