Question

我正在创建一个应用程序，使用下一个按钮显示字符串到下一个。但我的方法根本不显示字符串。我需要使用<TextView android:id="@+id/fact" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginBottom="246dp" android:text=" " app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toBottomOf="@+id/header" />方法吗？

public class FunFactsActivity extends AppCompatActivity {
    Button back;
    Button next;
    TextView fact;
    private List<String> listOfFacts;

    @Override
    protected void onCreate( Bundle savedInstanceState) {
        setContentView(R.layout.activity_fun_facts);
        super.onCreate(savedInstanceState);
        fact = findViewById(R.id.fact);
        back = findViewById(R.id.back);
        next = findViewById(R.id.next);
        listOfFacts = new ArrayList<>();

        //adds facts to the listOfFacts.
        for (int i = 0; i < new Database().facts.length; i++) {
            listOfFacts.add(new Database().facts[i]);
        }
        final String firstFact = listOfFacts.get(0);

        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String nextFact;
                nextFact = firstFact+1;
                displayFact(nextFact);
            }
        });
    }
    public String displayFact(String fact){
        return fact;
    }// display all of the facts one at a time, in order, go to the next one using the "next" button.

}

活动代码

import asyncio
import asyncpg
import requests

class node_http_mtr():
    def __init__(self, ip, nsrc, ndst):
        self.ip = ip
        self.nsrc = nsrc
        self.ndst = ndst
        try:
            self.data = requests.get('http://' + self.ip + '/nph-cgi_mtr?duration=-1&interval=0', stream=True, timeout=10)
        except:
            return

    def __iter__(self):
        return self

    def __next__(self):
        mtr = list()
        try:
            for chunk in self.data.iter_content(32 * (self.nsrc + self.ndst), '\n'):
                # DEBUG log chunk
                for line in chunk.split('\n'):
                    # DEBUG log line
                    if line.startswith('MTR'):
                        try:
                            _, io, num, val = line.split(' ')
                            l, r = val.split(':')[1], val.split(':')[2]
                            mtr.append((self.ip, io+num, l, r))
                        except:
                            # ERROR log line
                            pass
                        if len(mtr) == self.nsrc + self.ndst:
                            break
                if len(mtr) == self.nsrc + self.ndst:
                    yield mtr
                else:
                    continue
        except:
            # ERROR connection lost
            return


async def save_to_db(data_to_save):
    global pool
    try:
        async with pool.acquire() as conn:
            await conn.execute('''INSERT INTO mtr (ip, io, l, r) VALUES %s''' % ','.join(str(row) for row in data_to_save))
    finally:
        await pool.release(conn)


async def remove_from_db(ip):
    global pool
    try:
        async with pool.acquire() as conn:
            await conn.execute('''DELETE FROM httpmtr WHERE ip = $1''', ip)
    finally:
        await pool.release(conn)


async def http_mtr_worker():
    global workers_list
    global loop
    while True:
        await asyncio.sleep(0)
        for ip in list(workers_list):
            data_to_save = next(workers_list[ip])
            if data_to_save:
                asyncio.ensure_future(save_to_db(next(data_to_save)))
            await asyncio.sleep(0)


async def check_for_workers():
    global workers_list
    global pool
    while True:
        await asyncio.sleep(0)
        try:
            async with pool.acquire() as conn:
                workers = await conn.fetch('''SELECT ip FROM httpmtr''')
        finally:
            await pool.release(conn)
        for worker in workers:
            if worker['ip'] not in list(workers_list):
                workers_list[worker['ip']] = node_http_mtr(worker['ip'], 8, 8)
                await asyncio.sleep(0)
                print('Add worker', worker['ip'])
            await asyncio.sleep(0)
        ips_to_delete = set(workers_list.keys()) - set([i[0] for i in workers])
        if len(ips_to_delete) != 0:
            for ip in ips_to_delete:
                print('Delete worker ', ip)
                workers_list.pop(ip)
                await asyncio.sleep(0)


async def make_db_connection():
    pool = await asyncpg.create_pool(user='postgres', password='data', database='test', host='localhost', max_queries=50000, command_timeout=60)
    return pool


loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
pool = loop.run_until_complete(make_db_connection())
workers_list = {}
try:
    asyncio.ensure_future(check_for_workers())
    asyncio.ensure_future(http_mtr_worker())
    loop.run_forever()
except Exception as e:
    print(e)
    pass
finally:
    print("Closing Loop")
    loop.close()

Answer 1

这是你的问题：

public String displayFact(String fact){
    return fact; 
}

更改为：

public void displayFact(String fact){
    this.fact.setText(fact); 
}

另外，宣布一个计数器作为班级成员来跟踪你的事实：

private int counter;

@Override
protected void onCreate( Bundle savedInstanceState) {
    ...
    counter = 0;

    next.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            counter += 1
            String nextFact = listOfFacts.get(counter);
            displayFact(nextFact);
        }
    });

如何使用按钮显示字符串并更改为下一个字符串（在列表中）？

1 个答案: